Method and apparatus of multibeam optical disc readout

ABSTRACT

An optical pickup applies five different light beams at the same time to every second five tracks on a signal plane of a CD-ROM. A record data read system reads record data independently for each light beam system in accordance with outputs of respective light beams reflected from the signal plane, and stores the read record data in the record order. Under the control of a system controller, the optical pickup and record data read system read the record data of the CD-ROM by alternately performing an operation of continuously reading the record data with the five light beam systems during approximately two rotations of the CD-ROM and a track jump operation by seven tracks in a forward direction after the continuous reading operation with a combination of the five light beam systems shows no omission of the record data of the CD-ROM.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disc read apparatus andmethod, and more particularly to an optical disc read apparatus andmethod in which different light beams are applied at the same time to aplurality of adjacent tracks of an optical disc formed with a spiraltrack, such CD-ROM, CD-WO, DVD, DVD-ROM, and DVD-RAM, and data recordedon the tracks applied with the light beams are read with a record dataread system in accordance with a detected output of each reflected lightbeam.

2. Description of the Related Art

A multibeam method is one of the methods of reading record data from aCD-ROM at high speed. With this method, different light beams areapplied at the same time to a plurality of adjacent tracks of an opticaldisc formed with a spiral track, data recorded on the tracks appliedwith the light beams are read with a record data read system inaccordance with a detected output of each reflected light beam, and theread data are sequentially output in the record order by preventing theread data from being duplicated or omitted.

A multibeam method of reading an optical disc (CD-ROM) will be describedwith reference to FIG. 21. Reference numeral 1 represents an opticaldisc (CD-ROM) as viewed toward a signal plane (from an optical pickupside), CD-ROM being formed with a spiral track recorded with data (theouter and inner circumference sides of CD-ROM are indicated by arrows inFIG. 21). Reference numeral 2 represents an optical pickup capable ofradiating five light beams, the optical pickup 2 being provided with arelative rotation to CD-ROM 1 and moved from the inner circumference toouter circumference as record data read advances. As the optical pickup2 reaches a position I and starts reading record data, light beams 3 ₁to 3 ₅ are applied at the same time to respective tracks (x−1) to (x+3)and data recorded on the tracks applied with the light beams 3 ₁ to 3 ₅are read with a record data read system in accordance with a detectedoutput of each reflected light beam.

Record data of CD-ROM 1 is formed on the basis of one frame unit (oneframe=1/75 sec) represented by A-time (Absolute-time) of a sub-code Qchannel, in conformity with the CD signal format. As the optical pickup2 starts reading data from the position I shown in FIG. 21, the opticalbeam 3 ₁ system correctly reads record data from the frame ofA-time=23:40:59 or 23 minutes, 40 seconds, 59 frames, the optical beam 3₂ system correctly reads record data from the frame of A-time=23:40:74,the optical beam 3 ₃ system correctly reads record data from the frameof A-time=23:41:14, the optical beam 3 ₄ system correctly reads recorddata from the frame of A-time=23:41:29, and the optical beam 3 ₅ systemcorrectly reads record data from the frame of A-time=23:41:44.

As CD-ROM 1 rotates generally once (slightly more than once) and theread position with the optical pickup 2 reaches a position II shown inFIG. 21 (the light beams 3 ₁ to 3 ₅ are applied to the tracks x to(x+4), the optical beam 3 ₁ correctly reads record data up to the frameof A-time=23:40:73, the optical beam 3 ₂ correctly reads record data upto the frame of A-time=23:41:13, the optical beam 3 ₃ correctly readsrecord data up to the frame of A-time=23:41:28, and the optical beam 3 ₄correctly reads record data up to the frame of A-time=23:41:43. In thismanner, there is no omission of read data by the optical beams 3 ₁ to 3₅ (at this time, the light beam 3 ₅ has correctly read record data up tothe frame of A-time=23:41:58). The data read by the optical beams 3 ₁ to3 ₅ are output to external circuits in the record order by preventingthe read data from being duplicated.

When the read position with the optical pickup 2 reaches the position IIshown in FIG. 21, the optical pickup 2 is jumped forward (toward theouter circumference of CD-ROM 1) by three tracks. Namely, the opticalpickup 2 is jumped to a position III shown in FIG. 21 (and the lightbeams 3 ₁ to 3 ₅ are applied to tracks (x+3) to (x+7)). Thereafter, dataread starts again. Specifically, the optical beam 3 ₁ system correctlyreads record data from the frame of A-time=23:41:46, the optical beam 3₂ system correctly reads record data from the frame of A-time=23:41:61,the optical beam 3 ₃ system correctly reads record data from the frameof A-time=23:42:01, the optical beam 3 ₄ system correctly reads recorddata from the frame of A-time=23:42:16, and the optical beam 3 ₅ systemcorrectly reads record data from the frame of A-time=23:42:31.

As CD-ROM 1 rotates generally once (slightly more than once) and theread position with the optical pickup 2 reaches a position IV shown inFIG. 21 (the light beams 3 ₁ to 3 ₅ are applied to the tracks (x+4) to(x+8), the optical beam 3 ₁ system correctly reads record data up to theframe of A-time=23:41:60, the optical beam 3 ₂ system correctly readsrecord data up to the frame of A-time=23:42:00, the optical beam 3 ₃system correctly reads record data up to the frame of A-time=23:42:15,and the optical beam 3 ₄ system correctly reads record data up to theframe of A-time=23:42:30. In this manner, there is no omission of readdata by the optical beams 3 ₁ to 3 ₅ (at this time, the light beam 3 ₅has correctly read record data up to the frame of A-time=23:42:45). Thedata read by the optical beams 3 ₁ to 3 ₅ are output to the externalcircuits in the record order by preventing the read data from beingduplicated.

When the read position with the optical pickup 2 reaches the position IVshown in FIG. 21, the optical pickup 2 is jumped forward (toward theouter circumference of CD-ROM 1) by three tracks. Namely, the opticalpickup 2 is jumped to a position V shown in FIG. 21 (and the light beams3 ₁ to 3 ₅ are applied to tracks (x+7) to (3+11)). Thereafter, data readstarts again. Specifically, the optical beam 3 ₁ system correctly readsrecord data from the frame of A-time=23:42:33, the optical beam 3 ₂system correctly reads record data from the frame of A-time=23:42:48,the optical beam 3 ₃ system correctly reads record data from the frameof A-time=23:42:63, the optical beam 3 ₄ system correctly reads recorddata from the frame of A-time=23:43:03, and the optical beam 3 ₅ systemcorrectly reads record data from the frame of A-time=23:43:18.

As CD-ROM 1 rotates generally once (slightly more than once) and theread position with the optical pickup 2 reaches a position VI shown inFIG. 21 (the light beams 3 ₁ to 3 ₅ are applied to the tracks (x+8) to(x+12), the optical beam 3 ₁ system correctly reads record data up tothe frame of A-time=23:42:47, the optical beam 3 ₂ system correctlyreads record data up to the frame of A-time=23:42:62, the optical beam 3₃ system correctly reads record data up to the frame of A-time=23:43:02,and the optical beam 3 ₄ system correctly reads record data up to theframe of A-time=23:43:17. In this manner, there is no omission of readdata by the optical beams 3 ₁ to 3 ₅ (at this time, the light beam 3 ₅has correctly read record data up to the frame of A-time=23:43:32). Thedata read by the optical beams 3 ₁ to 3 ₅ are output to the externalcircuits in the record order by preventing the read data from beingduplicated.

When the read position with the optical pickup 2 reaches the position VIshown in FIG. 21, the optical pickup 2 is jumped forward (toward theouter circumference of CD-ROM 1) by three tracks. Namely, the opticalpickup 2 is jumped to a position VII shown in FIG. 21 (and the lightbeams 3 ₁ to 3 ₅ are applied to tracks (3+11) to (x+15)). Thereafter,data read starts again. Specifically, the optical beam 3 ₁ systemcorrectly reads record data from the frame of A-time=23:43:20, theoptical beam 3 ₂ system correctly reads record data from the frame ofA-time=23:43:35, the optical beam 3 ₃ system correctly reads record datafrom the frame of A-time=23:43:50, the optical beam 3 ₄ system correctlyreads record data from the frame of A-time=23:43:65, and the opticalbeam 3 ₅ system correctly reads record data from the frame ofA-time=23:44:05.

As CD-ROM 1 rotates generally once (slightly more than once) and theread position with the optical pickup 2 reaches a position VIII shown inFIG. 21 (the light beams 3 ₁ to 3 ₅ are applied to the tracks (x+12) to(x+16), the optical beam 3 ₁ system correctly reads record data up tothe frame of A-time=23:43:34, the optical beam 3 ₂ system correctlyreads record data up to the frame of A-time=23:43:49, the optical beam 3₃ system correctly reads record data up to the frame of A-time=23:43:64,and the optical beam 3 ₄ system correctly reads record data up to theframe of A-time=23:44:04. In this manner, there is no omission of readdata by the optical beams 3 ₁ to 3 ₅ (at this time, the light beam 3 ₅has correctly read record data up to the frame of A-time=23:44:19). Thedata read by the optical beams 3 ₁ to 3 ₅ are output to the externalcircuits in the record order by preventing the read data from beingduplicated.

While the optical pickup 2 is given a relative rotation to CD-ROM 1 fromthe position I to the position II, the light beam 3 ₅ system reads therecord data from the frame of A-time=23:41:44 to the frame ofA-time=23:41:58, whereas while the optical pickup 2 is given a relativerotation to CD-ROM 1 from the position III to the position IV, the lightbeam 3 ₁ system reads the record data from the frame of A-time=23:41:46to the frame of A-time=23:41:60. Therefore, record data from the frameof A-time=23:41:46 to the frame of A-time=23:41:58 is duplicated.Therefore, for the record data from the frame of A-time=23:41:46 to theframe of A-time=23:41:58, the record data previously read with the lightbeam 3 ₅ is output and the record data read with the light beam 3 ₁ isdiscarded.

When the track jump is performed from the position II shown in FIG. 21,the optical pickup 2 is jumped not by four tracks, but by three tracksin order to apply the light beam 3 ₁ to the track (x+3) from which therecord data was read with the light beam 3 ₅ system immediately beforethe track jump. If the number of jump tracks is “4”, the optical pickup2 is jumped to a position III′ shown in FIG. 21, and thereafter thelight beam 3 ₁ system reads record data from the frame ofA-time=23:41:61. Therefore, the record data in the frames ofA-time=23:41:59 and A-time=23:41:61 still not read with the light beam 3₅ before the track jump are omitted.

Generally, high speed read of CD-ROM 1 is performed by repeating anoperation of reading record data with n (n is an integer “3” or larger)light beam systems for one rotation and then making the optical pickupjump forward by (n−2) tracks.

When a track jump is performed, the focus servo system and trackingservo system are temporarily disturbed so that record data read cannotresume until these servo systems become stable.

With the conventional multibeam optical disc read method describedabove, if the number n of light beams is “5”, it is necessary to performa continuous read by about four rotations of CD-ROM 1 and three trackjumps in order to read record data from the tracks (x−1) to (x+16) shownin FIG. 21. Since a fairly long time is necessary for each track jump,it takes a long time to read data recorded in a number of tracks.

Record data read with some light beam systems may become impossiblebecause of a track pitch variation, surface vibration, center deviationand the like of CD-ROM 1. In such a case, the conventional optical discread method of repeating an operation of reading record data with n (nis an integer “3” or larger) light beam systems for approximately onerotation and then making the optical pickup jump forward by (n−2)tracks, is associated with some problem. For example, if the light beam3 ₂ system shown in FIG. 21 is unable to read record data, the recorddata in the frames from A-time=23:40:74 to A-time=23:41:13 cannot beread during the record data read with the optical pickup 2 byapproximately one rotation from the position I shown in FIG. 21.

As the optical pickup 2 reaches the position II, the track jump by threetracks to the position III is performed. Therefore, the record data inthe frames from A-time=23:40:74 to A-time=23:41:13 cannot be read. Also,the record data in the frames from A-time=23:41:61 to A-time=23:42:00cannot be read during the record data read by approximately one rotationfrom the position III.

As above, a problem occurs that a user cannot acquire a portion ofnecessary data.

SUMMARY OF THE INVENTION

It is an object of the present invention to solve the above problem andprovide an optical disc read method and apparatus capable of readingdata at high speed from an optical disc.

It is another object of the present invention to provide an optical discread method and apparatus capable of acquiring necessary data even ifdata read with some light beams is impossible.

It is a further object of the present invention to provide an opticaldisc read method and apparatus capable of efficiently reading recorddata from an optical disc even if data read with some light beams isimpossible.

In an optical disc read method according to the invention, data recordedon tracks of an optical disc formed with a spiral track is read with arecord data read system by applying different light beams 1, . . . , nat the same time to n tracks at every (c+1)-th and independentlydetecting the light beams reflected from the optical disc, where c is aninteger of 1 or larger and n is an integer of 2 or larger, and therecord data of the optical disc is read by alternately performing anoperation of continuously reading the record data on the tracks of theoptical disc with n light beam systems and a track jump operation in aforward direction after the continuous reading operation.

The continuous reading operation may be performed during approximately(c+1) rotations of the optical disc, and the track jump operation jumpsapproximately {(c+1) (n−1)−1} tracks in the forward direction.

If there is a light beam system unable to read the record data of theoptical disc, among the n light beam systems, the record data of theoptical disc may be read by alternately performing an operation ofcontinuously reading the record data on the tracks of the optical discwith n light beam systems during approximately (c+1) rotations and atrack jump operation by approximately {(c+1)·(M−1)−1} tracks in aforward direction after the continuous reading operation, by usingdetection outputs from only M (M<n) adjacent record data readable lightbeam systems.

M is the maximum number of adjacent record data readable light beamsystems among record data readable light beam systems.

Alternatively, if there is a light beam system unable to read the recorddata of the optical disc, among the n light beam systems and if Q is 2or larger and R is 0 or larger, where Q is the number of tracksrepresenting a distance between the innermost light beam and outermostlight beam among record data readable light beam systems and R is themaximum number of adjacent record data unreadable light beams betweenthe innermost and outermost record data readable light beams, the recorddata of the optical disc may be read by alternately performing anoperation of continuously reading the record data on the tracks of theoptical disc with the record data readable light beam systems duringapproximately {(R+1)·(c+1)} and a track jump operation by approximately(Q−1) tracks in a forward direction after the continuous readingoperation with a combination of the record data readable light beamsystems shows no omission of the record data of the optical disc.

The record data detected from the tracks of the optical disc during thecontinuous reading operation may be stored together with frameaddresses, and the track jump operation may be performed when a frameaddress corresponding to the record data read with the i-th light beambecomes continuous with a continuous data read start frame addresscorresponding to the record data to be read with the adjacent (i+1)-thlight beam.

According to another aspect of the optical disc read method of thisinvention, data recorded on tracks of an optical disc formed with aspiral track is read with a record data read system by applyingdifferent light beams at the same time to n tracks at every (c+1)-th andindependently detecting the light beams reflected from the optical disc,where c is an integer of 1 or larger and n is an integer of 2 or larger;a system capable of reading the record data from the optical disc isdetected from n light beam systems by applying the light beams topredetermined positions of the tracks of the optical disc at a start ofa continuous data reading operation and continuously reading the recorddata; and each light beam is set so that one of the detected record datareadable systems is applied to a read start track frame.

After each light beam is set so that one of the detected record datareadable systems is applied to a read start track frame, the record dataof the optical disc may be read by alternately performing an operationof continuously reading the record data during a predetermined number ofrotations of the optical disc and a track jump operation by apredetermined number of tracks, the rotation number and the track numberbeing determined in accordance with the number and layout of the recorddata readable systems.

The predetermined positions of the tracks of the optical disc may bepositions more in a backward direction than the read start track frame.

In an optical disc read apparatus embodying the optical disc readmethod, record data reading means includes a memory for storing therecord data obtained during the continuous reading operation and acorresponding frame address, and read control means performs the trackjump operation when a frame address corresponding to the record dataread with the i-th light beam becomes continuous with a continuous dataread start frame address corresponding to the record data to be readwith the adjacent (i+1)-th light beam.

According to the invention, since the continuous read of an optical discis performed approximately during (c+1) rotations, the number of trackjumps which take a long process time can be reduced so that record dataof the optical disc in a desired area can be read quickly.

Even if the record data cannot be read with some light beam systemsbecause of a track pitch variation, surface vibration, center deviationand the like of an optical disc, desired data of the optical disc can beread reliably and quickly with some or all the remaining record datareadable light beam systems by preventing the record data from beingomitted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a CD-ROM read apparatus embodying anoptical disc read method according to an embodiment of the invention.

FIG. 2 is a block diagram showing the structure of a parallel-to-serialconverter shown in FIG. 1.

FIG. 3 is a diagram illustrating an example of the contents of a memoryshown in FIG. 2.

FIG. 4 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 5 is a diagram illustrating an example of the contents of thememory shown in FIG. 2.

FIG. 6 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 7 is a diagram illustrating an example of the contents of thememory shown in FIG. 2.

FIG. 8 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 9 is a diagram illustrating an example of the contents of thememory shown in FIG. 2.

FIG. 10 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 11 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 12 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 13 is a diagram illustrating an example of the contents of thememory shown in FIG. 2.

FIG. 14 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 15 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 16 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 17 is a diagram illustrating an example of the contents of thememory shown in FIG. 2.

FIG. 18 is a diagram illustrating an example of a data read operation ofthe CD-ROM read apparatus shown in FIG. 1.

FIG. 19 is a diagram illustrating an example of the contents of thememory shown in FIG. 2.

FIGS. 20-1 and 20-2 are diagrams showing the structure of opticalpickups according to another embodiment of the invention.

FIG. 21 is a diagram illustrating a multibeam optical disc read method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, an embodiment of the invention will be described with reference toFIG. 1.

FIG. 1 is a block diagram of a CD-ROM read apparatus embodying anoptical disc read method according to an embodiment of the invention. InFIG. 1, like elements to those shown in FIG. 21 are represented by usingidentical reference numerals and characters.

Referring to FIG. 1, reference numeral 1 represents a CD-ROM formed witha spiral track recorded with data (the outer and inner circumferencesides of CD-ROM are indicated by arrows in FIG. 1). CD-ROM 1 is rotatedat a constant linear velocity with an unrepresented spindle motor.Reference numeral 2 represents an optical pickup of a multibeam type.The optical pickup 2 applies light beams 3 ₁ to 3 _(n) (n is the totalnumber of tracks applied with light beams) at the same time to every(c+1)-th tracks of CD-ROM 1, each reflected light beam is detected(received) with photodetectors PD₁ to PD_(n) which output photocurrentsas detection signals. c is an integer of “1” or larger and n is aninteger of “3” or larger. It is assumed here by way of example that c=1and n=5 (refer to FIG. 4).

In the optical pickup 2, reference numeral 4 represents a laser diodefor radiating a laser beam 3. Reference numeral 5 represents a grating(diffraction grating) for diffracting the laser beam to form a −2 orderdiffraction light beam 3 ₁, a −1 order diffraction light beam 3 ₂, a 0order diffraction light beam 3 ₃, a +1 order diffraction light beam 3 ₄,and a +2 order diffraction light beam 3 ₅. Reference numeral 6represents a beam splitter made of two rectangular prisms gluedtogether. Reference numeral 7 represents a collimator lens forconverting each diffused light beam into a collimated light beam.Reference numeral 8 represents an objective lens for focussing the lightbeams 3 ₁ to 3 ₅ passed through the beam splitter 6 and collimator lens7 onto a signal plane 1A of CD-ROM 1. Reference numeral 9 represents afocus actuator for moving the objective lens 8 along a directionperpendicular to the signal plane Al of CD-ROM 1 to follow a surfacevibration of CD-ROM 1, in order to maintain an in-focus state of thelight beam 3 ₁ to 3 ₅ relative to the signal plane 1A irrespective ofsurface vibrations of CD-ROM 1. Reference numeral 10 represents atracking actuator for moving the objective lens 8 along a radialdirection of the signal plane Al of CD-ROM 1 to follow a centerdeviation of CD-ROM 1, in order to make each light beam 3 ₁ to 3 ₅correctly trace a corresponding track. The focus actuator 9 and trackingactuator 10 are independently driven by a servo circuit to be describedlater.

The photodetectors PD₁ to PD₅ are provided in correspondence with thelight beams 3 ₁ to 3 ₅, and each outputs a photocurrent proportional toa received light amount. The light beams 3 ₁, 3 ₂, 3 ₄, and 3 ₅reflected from the signal plane A of CD-ROM 1 pass through the objectivelens 8 and collimator lens 7 and are reflected by the beam splitter 6.Thereafter, they pass through an optical system (not shown) including acylindrical lens, a detector lens and the like and become incident uponthe corresponding photodetectors PD₁, PD₂, PD₄, and PD₅. Thephotodetectors PD₁, PD₂, PD₄, and PD₅ output photocurrents I₁. I₂, I₄,and I₅ proportional to received light amounts, as detected outputs ofthe respective light beams 3 ₁, 3 ₂, 3 ₄, and 3 ₅. The photodetector PD₃is a four-division photodiode similar to that used for an optical pickupof the ordinary one beam type, and outputs photocurrents I₃-A, I₃-B,I₃-C, and I₃-D proportional to received light amounts of respectivedivision diodes.

Reference numeral 11 represents a sled motor for moving the opticalpickup 2 in the radial direction of CD-ROM 1 during a read or searchoperation. The sled motor is driven with the servo circuit and moves theoptical pickup 2 to a desired position along a forward or reversedirection during the search operation, or gradually moves the opticalpickup 2 along the forward direction during the read operation as theread operation of CD-ROM 1 advances.

Reference numeral 20 represents a record data read system which reads atthe same time the record data recorded on the tracks applied with thelight beams 3 ₁ to 3 ₅, from the light reception outputs of thephotodetectors PD₁ to PD₅ of the optical pickup 2, and serially outputsthe read record data in the record order of CD-ROM 1 by preventing theread record data from being duplicated or omitted. In the record dataread system 20, current/voltage converters (I/V) 21 ₁, 21 ₂, 21 ₄, and21 ₅ convert the photocurrents I₁, I₂, I₄, and I₅ output from thephotodetectors PD₁, PD₂, PD₄, and PD₅ into RF voltage signals RF₁, RF₂,RF₄, and RF₅ corresponding to the light beams 3 ₁, 3 ₂, 3 ₄, and 3 ₅ andoutput them. Current/voltage converters (I/V) 21 ₃-A, 21 ₃-B, 21 ₃-C,and 21 ₃-D convert the photocurrents I₃-A, I₃-B, I₃-C, and I₃-D outputfrom the photodetector PD₃ into voltage values V_(A), V_(B), V_(C), andV_(D) and output them.

Reference numeral 22 represents a computation section which performs anarithmetic operation of (V_(A)+V_(B)+V_(C)+V_(D)) to output an RF signalRF₃ corresponding to the light beam 3 ₃, an arithmetic operation of(V_(A)+V_(C))−(V_(B)+V_(D)) to output a focus error signal FE, and anarithmetic operation of (V_(A)+V_(B))−(V_(C)+V_(D)) to output a trackingerror signal TE. Reference numeral 23 represents the servo circuit forperforming a focus servo control, a tracking servo control, and a sledservo control. In accordance with the focus error signal FE, the focusactuator 9 is driven so as to make FE zero and focus the light beams 3 ₁to 3 ₅ upon the signal plane 1A, and in accordance with the trackingerror signal TE, the tracking actuator 10 is driven to make TE zero andmake (on-track) the light beams 3 ₁ to 3 ₅ trace the correspondingtracks.

Reference numerals 24 ₁ to 24 ₅ represent waveshape equalizers forincreasing the high frequency components of the RF signals RF₁ to RF₅ tothereby compensate for high frequency attenuation to be caused by thespatial transmission frequency (MTF) characteristics of the light beams3 ₁ to 3 ₅ and suppress the generation of inter-code interference. TheRF signal RF₃ input to the waveshape equalizer 24 ₃ or the RF signal RF₃output from the waveshape equalizer 24 ₃ is input to the servo circuit23. The servo circuit 23 activates the focus servo control uponjudgement of a timing when the value of the focus error signal FE entersa negative feedback region of the focus servo control during a focussearch operation. The servo circuit 23 activates the tracking servocontrol upon judgement of a timing by using the RF signal RF₃ when thelight beam 3 ₃ enters the negative region of the tracking servo control.

Reference numerals 26 ₁ to 26 ₅, represent first signal processingcircuits for performing binarization, clock recovery using PLL circuits,bit demodulation, frame sync detection, EFM demodulation, and sub-codedemodulation, by using the RF signals RF₁ to RF₅, and outputting dataDATA₁ to DATA₅ (inclusive of P, Q parities) after the EFM demodulationon the basis of one block unit (unit of 98 frames completing onesub-code frame), together with corresponding A-time data AT₁ to AT₅ ofthe sub-code Q channel. The first signal processing circuits 26 ₁ to 26₆ serially output the demodulated data DATA₁ to DATA₅ one symbol (8bits) after another. Upon detection of frame sync, the first signalprocessing circuits 26 ₁ to 26 ₅ output frame sync detection signals FS₁to FS₅ of H level to a system controller to be described later. Theseframe sync detection signals FS₁ to FS₅ are used for judging whetherdata can be read or not for the respective light beam 3 ₁ to 3 ₅systems. A-time data AT₃ output from the first signal processing circuit263 is also input to the system controller. The first signal processingcircuit 26 ₃ for the RF signal RF₃ system includes a CLV control circuit(not shown) for making the frame sync signal be detected at apredetermined time interval. The CLV control circuit performs a CLVcontrol of an unrepresented spindle motor drive circuit to rotate CD-ROM1 at a constant linear velocity. Reference numeral 30 represents aparallel-to-serial converter (P/S) for receiving in parallel data of oneblock unit output from the first signal processing circuits 26 ₁ to 26 ₅and serially outputting them in the record order by preventing the datafrom being duplicated or omitted. The specific structure of the P/Sconverter 30 is shown in FIG. 2. In FIG. 2, reference numerals 32 ₁ to32 ₅ represent memories each having two storage areas, a first area anda second area, and provided in correspondence with a corresponding oneof the first signal processing circuits 26 ₁ to 26 ₅. The data DATA₁ toDATA₅ output from the first signal processing circuits 26 ₁ to 26 ₅ arestored in ones of the first and second areas. Each of the first andsecond areas has a capacity allowing the data DATA₁ to DATA₅ of asufficient number of block units to be stored therein. Referencenumerals 33 ₁ to 33 ₅ represent memories each having two storage areas,a first area and a second area, and provided in correspondence with acorresponding one of the first signal processing circuits 26 ₁ to 26 ₅.The A-time data AT₁ to AT₅ output from the first signal processingcircuits 26 ₁ to 26 ₅ are stored in ones of the first and second areas,together with start addresses A_(1S) to A_(5S) (or a_(1s) to a_(5s)) andend addresses A_(1e) to A_(5e) (or a_(1e) to a_(5e)) indicating thelocation of the corresponding data DATA₁ to DATA₅ in the memories 32 ₁to 32 ₅. Each of the first and second areas has a capacity allowing theA-time data AT₁ to AT₅ of a sufficient number of data sets to be storedtherein.

Reference numerals 31 ₁ to 31 ₅ represent write controllers provided incorrespondence with the first signal processing circuits 26 ₁ to 26 ₅.The write controllers 31 ₁ to 31 ₅ control to write the data DATA₁ toDATA₅ output from the first signal processing circuits 26 ₁ to 26 ₅ inthe first or second areas of the memories 32 ₁ to 32 ₅, and to write theA-time data AT₁ to AT₅ in the first or second areas of the memories 32 ₁to 32 ₅ together with the start addresses A_(1S) to A_(5S) (or a_(1s) toa_(5s)) and end addresses A_(1e) to A_(5e) (or a_(1e) to a_(5e))indicating the location of the corresponding data DATA₁ to DATA₅ in thememories 32 ₁ to 32 ₅.

The contents of memories 32 _(f) and 33 _(f) (where f=1 to 5) are shownin FIG. 3. In this example, a write controller 31 _(f) controls to write15 blocks of each set of data DATA_(f) (1) to DATAf (30) in the firstarea, and to write 15 blocks of each set of data DATAf (31) to DATAf(60) in the second area. In the first area of the memory 33 _(f) theA-time data for each block of the data DATA_(f) (1) to DATAf (30) arewritten as, for example, frames of 23:40:60 to 23:41:14, together with astart address A_(fs) (1) and an end address A_(fe) (1) to a startaddress A_(fs) (30) and an end address A_(fe) (30) indicating thelocation of the corresponding data DATA_(f) (1) to DATA_(f) (30) in thefirst area of the memory 32 _(f). In the second area of the memory 33_(f), the A-time data for each block of the data DATA_(f) (31) toDATA_(f) (60) are written as, for example, frames of 23:42:48 to23:43:02, together with a start address A_(fs) (1) and an end addressA_(fe) (1) to a start address A_(fS)(³⁰) and an end address A_(fe)(30)indicating the location of the corresponding data DATA_(f) (31) toDATA_(f) (60) in the second area of the memory 32 _(f).

Reference numeral 34 represents a read controller. With reference to theA-time data and the start addresses A_(1S) to A_(5s) (or a_(1s) toa_(5s)) and end addresses A_(1e) to A_(5e) (or a_(1e) to a_(5e)) storedin the memories 33 ₁ to 33 ₅, the read controller 34 reads the dataDATA₁ to DATA₅ stored in the memories 33 ₁ to 33 ₅ by preventing thedata from being duplicated or omitted, and serially outputs the data onesymbol after another in the record order (A-time order) of CD-ROM 1.Specific operations of the write controllers 31 ₁ to 31 ₅ and readcontroller 34 will be later described.

Returning back to FIG. 1, reference numeral 40 represents a secondsignal processing circuit. The second signal processing circuit 40receives the data serially output from the P/S converter 30, descramblesthe data in the unit of one block, and thereafter demodulates Lch andRch data in conformity with the CD-DA specification through errordetection/correction based on CIRC codes (error detection/correctionwith P parities, deinterleaveing, error detection/correction with Qparities). The second signal processing circuit 40 then demodulates theCD-ROM data from the Lch and Rch data by performing sync detection,descrambling, header detection, and error detection/correction with EDCand ECC codes in accordance with the CD-ROM specification, andthereafter outputs the CD-ROM data to an external host computer.

Reference numeral 50 represents a system controller made of amicrocomputer. For the search operation, the system controller 50operates to supply a search command to the servo circuit 23, and todrive the sled motor 11 for the search operation to thereby move theoptical pickup 2 along the forward or reverse direction of CD-ROM 1 to adesired position. For the read operation, the system controller 50operates to supply various servo-on commands to the servo circuit 23,and to focus the light beams 3 ₁ to 3 ₅ upon the signal plane 1A ofCD-ROM 1 to thereby trace the every (c+1)-th tracks (n=5). Each timerecord data is read from each track during a proper number of rotationsof two or three or more, the system controller 50 supplies the servocircuit 23 with a track jump command of jumping the optical pickup by apredetermined number of tracks in the forward direction.

At the start of a read operation, the system controller 50 monitors theframe sync detection signals FS₁ to FS₅ input from the first signalprocessing circuits 26 ₁ to 26 ₅, during one rotation of CD-ROM 1, tocheck whether or not any system of the light beams 3 ₁ to 3 ₅ cannotread record data because of a track pitch variation, surface vibration,center deviation and the like of CD-ROM 1. If all the frame syncdetection signals FS₁ to FS₅ are H and there is no system unable to readrecord data, the system controller supplies a general read/write commandto the P/S converter 30 to thereby read/write data output from the firstsignal processing circuit 26 ₁ to 26 ₅ to and from the memories 32 ₁ to32 ₅.

If the frame sync detection signal for one or a plurality of light beamsis L for a predetermined time (e.g., 1/75 sec or longer) and data cannotbe read, light beams 3 _(i), 3 _(j), 3 _(k), . . . to be used for thedata read are selected from the light beams 3 ₁ to 3 ₅, and a specificread/write command including read system information “i, j, k, . . . ”indicating the light beam systems to be used for the data read issupplied to the P/S converter 30 to thereby read/write data DATA_(i),DATA_(j), DATA_(k), . . . output from the first signal processingcircuit 26 _(i), 26 _(j), 26 _(k), . . . among the first signalprocessing circuits 26 ₁ to 26 ₅ to and from the memories 32 ₁ to 32 ₅.

The general read/write command or specific read/write command outputfrom the system controller 50 is input to the read controller 34 of theP/S converter 30 and transferred from the read converter 34 to the writecontrollers 31 ₁ to 31 ₅. Upon reception of the general read/writecommand at the start of the data read, the write controllers 31 ₁ to 31₅ control to write the data DATA₁ to DATA₅ output from all the firstsignal processing circuits 26 ₁ to 26 ₅ first in the first areas of thememories 32 ₁ to 32 ₅. Upon reception of an intercept command from theread controller 34, the read operation is intercepted until a resumecommand is received, and then the data is written in the second areas.Similarly, when the intercept command is received thereafter, the readoperation is intercepted, and when the resume command is received, datais written in the areas not used at the preceding time.

If the write controllers 31 ₁ to 31 ₅ receive the specific read/writecommand at the start of the data read, only the write controllers 31_(i), 31 _(j), 31 _(k), . . . indicated by the read system information“i, j, k, . . . ” operate to write the data DATA_(i), DATA_(j),DATA_(k), . . . output from the first signal processing circuits 26_(i), 26 _(j), 26 _(k), . . . first in the first areas of the memories32 _(i), 32 _(j), 32 _(k), . . . Upon reception of the intercept commandfrom the read controller 34, the read operation is intercepted until theresume command is received, and then the data is written in the secondareas. Similarly, when the intercept command is received thereafter, theread operation is intercepted, and when the resume command is received,data is written in the areas not used at the preceding read cycle.

After receiving the general read/write command (specific read/writecommand) from the system controller 50, the read controller 34 suppliesthe intercept command to the write controllers 31 ₁ to 31 ₅ (31 _(i), 31_(j), 31 _(k). . . ) and a jump command to the system controller 50,when all A-time data become continuous without omission in the areasamong the memories 33 ₁ to 33 ₅ (33 _(i), 33 _(j), 33 _(k), . . . )where data were written by the write controllers 31 ₁ to 31 ₅ (31 _(i),31 _(j), 31 _(k), . . . ) at the present read cycle. With reference tothe A-time data and the start and end addresses stored in the areasamong the memories 33 ₁ to 33 ₅ (33 _(i), 33 _(j), 33 _(k), . . . )where data were written at the present read cycle, the read controller34 controls to read and output record data in the order of A-timestarting from the oldest A-time, relative to the data stored in theareas among the memories 33 ₁ to 33 ₅ (33 _(i), 33 _(j) 33 _(k), . . . )where data were written at the present read cycle.

Thereafter, upon reception of a jump completion notice from the systemcontroller 50, the read controller 34 supplies the resume command to thewrite controllers 31 ₁ to 31 ₅ (31 _(i), 31 _(j), 31 _(k), . . . ).Thereafter, the read controller 34 supplies the intercept command to thewrite controllers 31 ₁ to 31 ₅ (31 _(i), 31 _(j), 31 _(k), . . . ) andthe jump command to the system controller 50, when all A-time databecome continuous without omission in the areas among the memories 33 ₁to 33 ₅ (33 _(i), 33 _(j), 33 _(k), . . . ) not used at the precedingread cycle. With reference to the A-time data and the start and endaddresses stored in the areas among the memories 33 ₁ to 33 ₅ (33 _(i),33 _(j), 33 _(k), . . . ) not used at the preceding read cycle, the readcontroller 34 controls to read and output record data in the order ofA-time starting from the A-time next to the A-time corresponding to theone block data lastly output to the second signal processing circuit atthe preceding read cycle, relative to the data stored in the areas amongthe memories 33 ₁ to 32 ₅ (32 _(i), 32 _(j), 32 _(k), . . . ) not usedat the preceding read cycle. Similar operations are repeated thereafter.

The operation of the embodiment will be described with reference toFIGS. 4 to 19. It is herein assumed that CD-ROM 1 rotates at a constantlinear velocity under CLV control and the focus servo is turned on, andthat different light beams 3 ₁ to 3 ₅ are applied at the same time toevery (c+1)-th tracks (n=5) of CD-ROM 1.

(1) Judgement of Unreadable System

When an unrepresented host computer designates a read start point ofCD-ROM 1 as a frame having A-time, for example, 23:41:0, the systemcontroller 50 determines the position of the track containing the readstart A-time frame of CD-ROM 1, the read start point being representedby x (refer to FIGS. 4, 6, 8, 10-12, 14-16, and 18). The systemcontroller 50 first supplies the search command to the servo circuit 23to move the optical pickup 2 so that the light beam 3 ₁ reaches theposition of the track (x−8). Thereafter, the system controller 50supplies a tracking servo-on command and a sled servo-on command to theservo circuit 23 to activate the tracking servo and sled servo.Therefore, the light beams 3 ₁ to 3 ₅ radiated from the optical pickup 2are focussed on the tracks (x−8), (x−6), (x−4), (x−2) and x in antrack-on state (refer to I in FIGS. 4, 6, 8, 10-12, 14-16, and 18).

The light beams 3 ₁ to 3 ₅ reflected by the signal plane 1A are receivedby the photodetectors PD₁ to PD₅ which output photocurrents I₁ to I₅ Ofthese photocurrents, the photocurrents I₁, I₂, I₄, and I₅ output fromthe photodetectors PD₁, PD₂, PD₄, and PD₅ are-converted into RF signalsRF₁, RF₂, RF₄, and RF₅ by the current-to-voltage converters 21 ₁, 21 ₂,21 ₄, and 21 ₅ which are waveshape equalized by the waveshape equalizers24 ₁, 24 ₂, 24 ₄, and 24 ₅ and input to the first signal processingcircuits 26 ₁, 26 ₂, 26 ₄, and 26 ₅. Photocurrents I₃-A to I₃-D from thephotodetector PD₃ are converted into voltage values V_(A) to V_(D) bythe current-to-voltage converters 21 ₃-A to 21 ₃-D and added together bythe computation section 22 to generate an RF signal RF₃. The RF signalRF₃ is waveshape equalized by the waveshape equalizer 24 ₃ and input tothe first signal processing circuit 26 ₃.

The first signal processing circuits 26 ₁ to 26 ₅ make the input RFsignals RF₁ to RF₅ be subjected to binarization, clock recovery usingPLL circuits, bit demodulation, frame sync detection, EFM demodulation,and sub-code demodulation, and outputs data DATA₁ to DATA₅ (inclusive ofP, Q parities) after the EFM demodulation on the basis of one blockunit, together with corresponding A-time data AT₁ to AT₅ of the sub-codeQ channel. The first signal processing circuits 26 ₁ to 26 ₆ seriallyoutput the demodulated data DATA₁ to DATA₅ one symbol (8 bits) afteranother. Upon detection of the frame sync signals, the first signalprocessing circuits 26 ₁ to 26 ₆ output the frame sync detection signalsFS₁ to FS₆ of H level to the system controller 50.

After the light beams 3 ₁ to 3 ₅ from the optical pickup 2 are focussedonto the tracks (x−8), (x−6), (x−4), (x−2), and x in the on-track stateby the search operation, the system controller monitors the frame syncdetection signals FS₁ to FS₅ input from the first signal processingcircuits 26 ₁ to 26 ₆ to judge a presence/absence of a record dataunreadable system, depending upon whether there is a system taking the Llevel for a predetermined time (in this example, one block=1/75 sec orlonger) during one rotation of CD-ROM 1.

(2) General Read/write Operation (Refer to FIGS. 4 and 5).

First, the description will be given for the case wherein record datacan be read with all the light beam 3 ₁ to 3 ₅ systems.

If the judgement of a presence/absence of a record data unreadablesystem shows that there is no record data unreadable system, as the readsystems of h light beams, all the five light beams 3 ₁ to 3 ₅ areallocated. A continuous read rotation number I is set as I=(c+1)=2, anda read track jump number J is set to J={(c+1) (c−1)−1}=7. In accordancewith the A-time data representative of the latest A-time data AT₃ inputfrom the first signal processing circuit 26 ₃ and the read start pointA-time designated by the host computer, the track jump direction andnumber are determined so that the light beam 3 ₁ at the innermostcircumference among the h=5 read light beams is focussed in the track-onstate on the track (x−1) one track inner than the track x containing theread start point of the A-time.

If the optical pickup 2 is at a position II shown in FIG. 4 after the hread light beam systems are allocated and the continuous read number Iand read track jump number J are set, the optical pickup 2 is jumpedfrom the position II by six tracks in the forward direction so that thelight beams 3 ₁ to 3 ₅ are focussed in the track-on state on the tracks(x−1), (x+1), (x+3), (x+5), and (x+7) (refer to III in FIG. 4). Then,reading the record data on the tracks (x−1), (x+1), (x+3), (x+5), and(x+7) at the same time starts, by using five systems including thephotodetector PD₁ to first signal processing circuit 26 ₁, photodetectorPD₂ to first signal processing circuit 26 ₂, photodetector PD₃ to firstsignal processing circuit 26 ₃, photodetector PD₄ to first signalprocessing circuit 264 ₂, and photodetector PD₅ to first signalprocessing circuit 26 ₅. When all the frame sync detection signals FS₁to FS₅ are input from the first signal processing circuits 26 ₁ to 26 ₅,the general read/write command is supplied to the P/S converter 30.

Upon reception of the general read/write command via the read controller34, the write controllers 31 ₁ to 31 ₅ write one block after another thedata DATA₁ to DATA₅ output from the first signal processing circuits 26₁ to 26 ₅, into the first areas of the memories 32 ₁ to 32 ₅, and writesthe A-time data AT₁ to AT₅ corresponding to the data DATA₁ to DATA₅ andthe pairs of start addresses A_(1S) to A_(5S) and end addresses A_(1e)to A_(5e) in the memories 32 ₁ to 32 ₅, into the first areas of thememories 33 ₁ to 33 ₅ (refer to FIG. 3). In the example shown in FIG. 4,in the first areas of the memories 33 ₁ to 3 ₃ ₅, the A-time data iswritten from the frames of 23:40:60, 23:41:15, 23:41:45, 23:42:00, and23:42:30 (refer to FIG. 5).

The read controller 34 received the general read/write command checkswhether there is no omission of record data read with each read system,by referring to the first areas of the memories 33 ₁ to 33 ₅ used at thepresent read cycle to confirm that the A-time one frame before the startA-time data in the first area of the memory 33 ₅ is contained in thefirst area of the memory 33 ₄, that the A-time one frame before thestart A-time data in the first area of the memory 33 ₄ is contained inthe first area of the memory 33 ₃, that the A-time one frame before thestart A-time data in the first area of the memory 33 ₃ is contained inthe first area of the memory 33 ₂, and that the A-time one frame beforethe start A-time data in the first area of the memory 33 ₂ is containedin the first area of the memory 33 ₁.

After the read operation by the optical pickup 2 is performedapproximately I=two rotations (in actual, slightly more than tworotations) and the optical pickup 2 reaches a position IV shown in FIG.4, the contents of the first areas of the memories 33 ₁ to 33 ₅ becomeas shown in FIG. 5 and there is no omission of record data read with theread systems. Therefore, the read controller 34 supplies the interceptcommand to the write controllers 31 ₁ to 31 ₅ to intercept the writeoperation, and supplies the track jump command to the system controller50. With reference to the A-time data and the start and end addressesstored in the first areas among the memories 33 ₁ to 33 ₅ where datawere written at the present read cycle, the read controller 34 controlsto read record data in the order of A-time starting from the oldestA-time, relative to the data stored in the first areas among thememories 33 ₁ to 33 ₅ where data DATA₁ to DATA₅ were written at thepresent read cycle, and outputs the read data to the second signalprocessing circuit 40. In this example, the data from the frame 23:40:60to the frame 23:42:59 is output. Since the read start point designatedby the host computer has the A-time at the frame of 23:41:00, the datais output starting from the frame immediately before the read startpoint.

The second signal processing circuit 40 receives the data seriallyoutput from the P/S converter 30, descrambles the data in the unit ofone block, and thereafter demodulates Lch and Rch data in conformitywith the CD-DA specification through error detection/correction based onCIRC codes (error detection/correction with P parities, deinterleaveing,error detection/correction with Q parities). The second signalprocessing circuit 40 then demodulates the CD-ROM data from the Lch andRch data by performing sync detection, descrambling, header detection,and error detection/correction with EDC and ECC codes in accordance withthe CD-ROM specification, and thereafter outputs the CD-ROM data to anexternal host computer.

The write controllers 31 ₁ to 31 ₅ received the intercept commandintercepts the read operation of the memories 32 ₁ to 32 ₅ and 33 ₁ to33 ₅. The system controller 50 received the track jump command suppliesthe servo circuit 23 with the track jump command indicating a track jumpby J=7 tracks in the forward direction to thereby jump the opticalpickup 2 from the position IV to a position V shown in FIG. 4. After thelight beams 3 ₁ to 3 ₅ are focussed in the track-on state on the tracks(x+8), (x+10), (x+12), (x+14), and (x+16), reading record data resumes.When all the frame sync detection signals FS₁ to FS₅ of H level areoutput from the first signal processing circuits 26 ₁ to 26 ₅, the trackjump completion notice is read and supplied to the controller 34.

The controller 34 received the track jump completion notice supplies theresume command to the write controllers 31 ₁ to 31 ₅, and the writecontrollers 31 ₁ to 31 ₅ received the resume command write the dataDATA₁ to DATA₅ output from the first signal processing circuits 26 ₁ to26 ₅ after the track jump, this time into the second areas of thememories 32 ₁ to 32 ₅, and writes the A-time data AT₁ to AT₅corresponding to the data DATA₁ to DATA₅ and the pairs of startaddresses a_(1S) to a_(5S). and end addresses a_(1e) to a_(5e) in thememories 32 ₁ to 32 ₅, into the second areas of the memories 33 ₁ to 33₅ (refer to FIG. 3). In the example shown in FIG. 4, in the second areasof the memories 33 ₁ to 33 ₅, the A-time data is written from the framesof 23:42:48, 23:43:03, 23:43:33, 23:43:63, and 23:44:18 (refer to FIG.5).

After the read controller 34 supplies the resume command, the readcontroller 34 checks whether there is no omission of record data readwith each read system of the h=5 read light beams, by referring to thesecond areas of the memories 33 ₁ to 33 ₅ used at the present read cycleto confirm that the A-time one frame before the start A-time data in thesecond area of the memory 33 ₅ is contained in the second area of thememory 33 ₄, that the A-time one frame before the start A-time data inthe second area of the memory 33 ₄ is contained in the second area ofthe memory 33 ₃, that the A-time one frame before the start A-time datain the second area of the memory 33 ₃ is contained in the second area ofthe memory 33 ₂, and that the A-time one frame before the start A-timedata in the second area of the memory 33 ₂ is contained in the secondarea of the memory 33 ₁.

After the read operation by the optical pickup 2 is performedapproximately I=two rotations (in actual, slightly more than tworotations) and the optical pickup 2 reaches a position VI shown in FIG.4, the contents of the second areas of the memories 33 ₁ to 33 ₅ becomeas shown in FIG. 5 and there is no omission of record data read with theread systems Therefore, the read controller 34 supplies the interceptcommand to the write controllers 31 ₁, to 31 ₅ to intercept the writeoperation, and supplies the track jump command to the system controller50. With reference to the A-time data and the start and end addressesstored in the second areas among the memories 33 ₁ to 33 ₅ where datawere written at the present read cycle, the read controller 34 controlsto read record data in the order of A-time starting from the A-time nextto the one block data lastly output to the second signal processingcircuit 40 at the preceding read cycle, relative to the data stored inthe second areas among the memories 32 ₁ to 32 ₅ where data DATA₁ toDATA₅ were written at the present read cycle, and outputs the read datato the second signal processing circuit 40. In this example, the datafrom the frame 23:42:60 to the frame 23:44:47 is output.

The write controllers 31 ₁ to 31 ₅ received the intercept commandintercepts the read operation of the memories 32 ₁ to 32 ₅ and 33 ₁ to33 ₅. The system controller 50 received the track jump command controlsto jump the optical pickup 2 from the position VI to a position VIIshown in FIG. 4. After the light beams 3 ₁ to 3 ₅ are focussed in thetrack-on state on the tracks (x+17), (x+19), (x+21), (x+23), and (x+25),reading record data resumes. When all the frame sync detection signalsFS₁ to FS₅ of H level are output from the first signal processingcircuits 26 ₁ to 26 ₅, the track jump completion notice is read andsupplied to the controller 34.

The controller 34 received the track jump completion notice via the readcontroller 34 controls to write the data DATA₁ to DATA₅ output from thefirst signal processing circuits 26 ₁ to 26 ₅ after the track jump, thistime into the first areas of the memories 32 ₁ to 32 ₅, and writes theA-time data AT₁ to AT₅ corresponding to the data DATA₁ to DATA₅ and thepairs of start addresses A₁ to A₅s and end addresses A_(1e) to A_(5e) inthe memories 32 ₁ to 32 ₅, into the first areas of the memories 33 ₁ to33 ₅. When all A-time data stored in the first areas of the memories 33₁ to 33 ₅ become continuous without omission, the read controller 34controls to read and output record data in the A-time order startingfrom the A-time next to the A-time corresponding to the one block datalastly output to the second signal processing circuit 40 at thepreceding read cycle, relative to the first areas of the memories 32 ₁to 32 ₅. Thereafter, similar operations are repeated to read at highspeed desired record data from CD-ROM 1 by preventing the record datafrom being duplicated and omitted.

Reading the tracks (x−1) to (x+17) shown in FIG. 4 requires a continuousread of CD-ROM by about two rotations and one track jump and can beexecuted at much more higher speed than the case illustrated in FIG. 20.

(3) First Specific Read/write Operation (Read Unable by the Light BeamSystem 3 ₅, Refer to FIGS. 6 and 7)

If the judgement of a presence/absence of a record data unreadablesystem during one relative rotation of the optical pickup 2 from aposition I shown in FIG. 6 relative to CD-ROM 1, shows that there is onerecord data unreadable system of the light beam 3 ₅ at the outermostcircumference, M=4 light beams 3 ₁ to 3 ₄ are allocated as the readsystems of h light beams, where M is the maximum number of adjacentlight beam systems usable, which is “4” or a combination of light beams3 ₁ to 3 ₄ and M≧2. The continuous read rotation number I is set asI=(c+1)=2, and the read track jump number J is set to J={(c+1)(M−1)−1}=5.

In accordance with the A-time data representative of the latest A-timedata AT₃ input from the first signal processing circuit 26 ₃ and theread start point A-time designated by the host computer, the track jumpdirection and number are determined so that the light beam 3 ₁ at theinnermost circumference among the h=4 read light beams is focussed inthe track-on state on the track (x−1) one track inner than the track xcontaining the read start point of the A-time.

If the optical pickup 2 is at a position II shown in FIG. 6 after the hread light beam systems are allocated and the continuous read number Iand read track jump number J are set, the optical pickup 2 is jumpedfrom the position II by six tracks in the forward direction so that thelight beams 3 ₁ to 3 ₄ are focussed in the track-on state on the tracks(x−1), (x+1), (x+3), and (x+5). Then, reading the record data on thetracks (x−1), (x+1), (x+3), and (x+5) at the same time starts, by usingfour systems including the photodetector PD₁ to first signal processingcircuit 26 ₁, photodetector PD₂ to first signal processing circuit 26 ₂,photodetector PD₃ to first signal processing circuit 26 ₃, andphotodetector PD₄ to first signal processing circuit 26 ₄. When all theframe sync detection signals FS₁ to FS₄ are input from the first signalprocessing circuits 26 ₁ to 26 ₄, the specific read/write commandincluding the read system information “1, 2, 3, 4” is supplied to theP/S converter 30.

Upon reception of the specific read/write command via the readcontroller 34, only the write controllers 31 ₁ to 31 ₄ indicated by theread system information “1, 2, 3, 4” write one block after another thedata DATA₁ to DATA₄ output from the first signal processing circuits 26₁ to 26 ₄, into the first areas of the memories 32 ₁ to 3 ₂ 4, andwrites the A-time data AT₁ to AT₄ corresponding to the data DATA₁ toDATA₄ and the pairs of start addresses A_(1S) to A_(4S) and endaddresses A_(1e) to A_(4e) in the memories 32 ₁ to 32 ₄, into the firstareas of the memories 33 ₁ to 33 ₄. In the example shown in FIG. 6, inthe first areas of the memories 33 ₁ to 33 ₄, the A-time data is writtenfrom the frames of 23:40:60, 23:41:15, 23:41:45, and 23:42:00 (refer toFIG. 7).

The read controller 34 received the specific read/write command checkswhether there is no omission of record data read with each read system,by referring to the first areas of the memories 33 ₁ to 33 ₄ indicatedby the read system information “1, 2, 3, 4” and used at the present readcycle to confirm that the A-time one frame before the start A-time datain the first area of the memory 33 ₄ is contained in the first area ofthe memory 33 ₃, that the A-time one frame before the start A-time datain the first area of the memory 33 ₃ is contained in the first area ofthe memory 33 ₂, and that the A-time one frame before the start A-timedata in the first area of the memory 33 ₂ is contained in the first areaof the memory 33 ₁.

After the read operation by the optical pickup 2 is performedapproximately I=two rotations (in actual, slightly more than tworotations) and the optical pickup 2 reaches a position IV shown in FIG.6, the contents of the first areas of the memories 33 ₁ to 33 ₄ becomeas shown in FIG. 7 and there is no omission of record data read with theread systems. Therefore, the read controller 34 supplies the interceptcommand to the write controllers 31 ₁ to 31 ₄ to intercept the writeoperation, and supplies the track jump command to the system controller50. With reference to the A-time data and the start and end addressesstored in the first areas among the memories 33 ₁ to 33 ₄ where datawere written at the present read cycle, the read controller 34 controlsto read record data in the order of A-time starting from the oldestA-time, relative to the data stored in the first areas among thememories 33 ₁ 1 to 33 ₄ where data DATA₁ to DATA₄ were written at thepresent read cycle, and outputs the read data to the second signalprocessing circuit 40. In this example, the data from the frame 23:40:60to the frame 23:42:29 is output.

The write controllers 3 ₁ to 314 received the intercept commandintercepts the read operation of the memories 32 ₁ to 32 ₄ and 33 ₁ to33 ₄. The system controller 50 received the track jump command suppliesthe servo circuit 23 with the track jump command indicating a track jumpby J=5 tracks in the forward direction to thereby jump the opticalpickup 2 from the position IV to a position V shown in FIG. 6. After thelight beams 3 ₅ to 3 ₄ are focussed in the track-on state on the tracks(x+6), (x+8), (x+10), and (x+12), reading record data resumes. When allthe frame sync detection signals FS₁ to FS₅ of H level are output fromthe first signal processing circuits 26 ₁ to 26 ₄, the track jumpcompletion notice is read and supplied to the controller 34.

The controller 34 received the track jump completion notice supplies theresume command to the write controllers 31 ₁ to 31 ₄ , and the writecontrollers 31 ₁ to 31 ₄ received the resume command write the dataDATA₁ to DATA₄ output from the first signal processing circuits 26 ₁ to26 ₄ after the track jump, this time into the second areas of thememories 32 ₁ to 3 ₂ 4, and writes the A-time data AT₁ to AT₄corresponding to the data DATA₁ to DATA₄ and the pairs of startaddresses a_(1s). to a_(4s) and end addresses a_(1e) to a_(4e) in thememories 32 ₁ to 32 ₄, into the second areas of the memories 33 ₁ to 33₄. In the example shown in FIG. 6, in the second areas of the memories33 ₁ to 33 ₄, the A-time data is written from the frames of 23:42:18,23:42:48, 23:43:03, and 23:43:33(refer to FIG. 7).

After the read controller 34 supplies the resume command, the readcontroller 34 checks whether there is no omission of record data readwith each read system, by referring to the second areas of the memories33 ₁ to 33 ₄ used at the present read cycle to confirm that the A-timeone frame before the start A-time data in the second area of the memory33 ₄ is contained in the second area of the memory 33 ₃, that the A-timeone frame before the start A-time data in the second area of the memory33 ₃ is contained in the second area of the memory 33 ₂, and that theA-time one frame before the start A-time data in the second area of thememory 33 ₂ is contained in the second area of the memory 33 ₁. Afterthe read operation by the optical pickup 2 is performed approximatelyI=two rotations (in actual, slightly more than two rotations) and theoptical pickup 2 reaches a position VI shown in FIG. 6, the contents ofthe second areas of the memories 33 ₁ to 33 ₄ become as shown in FIG. 7and there is no omission of record data read with the read systems “1,2, 3, 4”. Therefore, the read controller 34 supplies the interceptcommand to the write controllers 31 ₁ to 31 ₄ to intercept the writeoperation, and supplies the track jump command to the system controller50. With reference to the A-time data and the start and end addressesstored in the second areas among the memories 33 ₁ to 33 ₄ where datawere written at the present read cycle, the read controller 34 controlsto read record data in the order of A-time starting from the A-time nextto the one block data lastly output to the second signal processingcircuit 40 at the preceding read cycle, relative to the data stored inthe second areas among the memories 32 ₁ to 3 ₂ 4 where data DATA₁ toDATA₄ were written at the present read cycle, and outputs the read datato the second signal processing circuit 40. In this example, the datafrom the frame 23:42:30 to the frame 23:43:62 is output.

The write controllers 31 ₁ to 31 ₄ received the intercept commandintercepts the read operation. The system controller 50 received thetrack jump command controls to jump the optical pickup 2 from theposition VI to a position VII shown in FIG. 6. After the light beams 3 ₁to 3 ₄ are focussed in the track-on state on the tracks (x+13), (x+15),(x+17), and (x+19), reading record data resumes. When all the frame syncdetection signals FS₁ to FS₄ of H level are output from the first signalprocessing circuits 26 ₁ to 26 ₄, the track jump completion notice isread and supplied to the controller 34. Thereafter, similar operationsare repeated to read at high speed desired record data from CD-ROM 1 byusing the four beams 3 ₁ to 3 ₄ and by preventing the record data frombeing duplicated and omitted.

(4) Second Specific Read/write Operation (Read Unable by the Light BeamSystem 3 ₄, Refer to FIGS. 8 and 9)

If the judgement of a presence/absence of a record data unreadablesystem during one relative rotation of the optical pickup 2 from aposition I shown in FIG. 8 relative to CD-ROM 1, shows that there is onerecord data unreadable system of the light beam 34, M=3 light beams 3 ₁to 3 ₃ are allocated as the read systems of h light beams, where M isthe maximum number of adjacent light beam systems usable, which is “3”or a combination of light beams 3 ₁ to 3 ₃ and M≧2. The continuous readrotation number I is set as I=(c+1)=2, and the read track jump number Jis set to J={(c+1)·(M−1)−1}=3. In accordance with the A-time datarepresentative of the latest A-time data AT₃ input from the first signalprocessing circuit 26 ₃ and the read start point A-time designated bythe host computer, the track jump direction and number are determined sothat the light beam 3 ₁ at the innermost circumference among the h=3read light beams is focussed in the track-on state on the track (x−1)one track inner than the track x containing the read start point of theA-time.

If the optical pickup 2 is at a position II shown in FIG. 8 after the hread light beam systems are allocated and the continuous read number Iand read track jump number J are set, the optical pickup 2 is jumpedfrom the position II by six tracks in the forward direction so that thelight beams 3 ₁ to 3 ₄ are focussed in the track-on state on the tracks(x−1), (x+1), and (x+3). Then, reading the record data on the tracks(x−1), (x+1) and (x+3) at the same time starts, by using three systemsincluding the photodetector PD₁ to first signal processing circuit 26 ₁,photodetector PD₂ to first signal processing circuit 26 ₂, andphotodetector PD₃ to first signal processing circuit 26 ₃. When all theframe sync detection signals FS₁ to FS₃ are input from the first signalprocessing circuits 26 ₁ to 26 ₃, the specific read/write commandincluding the read system information “1, 2, 3” is supplied to the P/Sconverter 30.

Upon reception of the specific read/write command via the readcontroller 34, only the write controllers 311 to 313 indicated by theread system information “1, 2, 3” write one block after another the dataDATA₁ to DATA₃ output from the first signal processing circuits 26 ₁ to26 ₃, into the first areas of the memories 32 ₁ to 32 ₃, and writes theA-time data AT1 to AT₃ corresponding to the data DATA₁ to DATA₃ and thepairs of start addresses A_(1s) to A_(3s) and end addresses A_(1e) toA_(3e) in the memories 32 ₁ to 33 ₃, into the first areas of thememories 33 ₁ to 33 ₃. In the example shown in FIG. 8, in the firstareas of the memories 33 ₁ to 33 ₃, the A-time data is written from theframes of 23:40:60, 23:41:15, and 23:41:45 (refer to FIG. 9).

The read controller 34 received the specific read/write command checkswhether there is no omission of record data read with each read system,by referring to the first areas of the memories 33 ₁ to 33 ₃ indicatedby the read system information “1, 2, 3” and used at the present readcycle to confirm that the A-time one frame before the start A-time datain the first area of the memory 33 ₃ is contained in the first area ofthe memory 33 ₂, and that the A-time one frame before the start A-timedata in the first area of the memory 33 ₂ is contained in the first areaof the memory 33 ₁.

After the read operation by the optical pickup 2 is performedapproximately I=two rotations (in actual, slightly more than tworotations) and the optical pickup 2 reaches a position IV shown in FIG.8, the contents of the first areas of the memories 33 ₁ to 33 ₃ becomeas shown in FIG. 9 and there is no omission of record data read with theread systems. Therefore, the read controller 34 supplies the interceptcommand to the write controllers 31 ₁ to 31 ₃ to intercept the writeoperation, and supplies the track jump command to the system controller50. With reference to the A-time data and the start and end addressesstored in the first areas among the memories 33 ₁ to 33 ₃ where datawere written at the present read cycle, the read controller 34 controlsto read record data in the order of A-time starting from the oldestA-time, relative to the data stored in the first areas among thememories 33 ₁ to 33 ₃ where data DATA₁ to DATA₃ were written at thepresent read cycle, and outputs the read data to the second signalprocessing circuit 40. In this example, the data from the frame 23:40:60to the frame 23:41:74 is output.

The write controllers 31 ₁ to 31 ₄ received the intercept commandintercepts the read operation, and the system controller 50 received thetrack jump command supplies the servo circuit 23 with the track jumpcommand indicating a track jump by J=3 tracks in the forward directionto thereby jump the optical pickup 2 from the position IV to a positionV shown in FIG. 8. After the light beams 3 ₁ to 3 ₃ are focussed in thetrack-on state on the tracks (x+4), (x+6), and (x+8), reading recorddata resumes. When all the frame sync detection signals FS₁ to FS₃ of Hlevel are output from the first signal processing circuits 26 ₁ to 26 ₃,the track jump completion notice is read and supplied to the controller34.

The controller 34 received the track jump completion notice supplies theresume command to the write controllers 31 ₁ to 31 ₃, and the writecontrollers 31 ₁ to 31 ₃ received the resume command write the dataDATA₁ to DATA₃ output from the first signal processing circuits 26 ₁ to26 ₃ after the track jump, this time into the second areas of thememories 32 ₁ to 32 ₃, and writes the A-time data AT₁ to AT₃corresponding to the data DATA₁ to DATA₃ and the pairs of startaddresses a_(1s) to a_(3s) and end addresses a_(1e) to a_(3e) in thememories 32 ₁ to 32 ₃, into the second areas of the memories 33 ₁ to 33₃. In the example shown in FIG. 8, in the second areas of the memories33 ₁ to 33 ₃, the A-time data is written from the frames of 23:41:63,23:42:18, and 23:42:48 (refer to FIG. 9).

After the read controller 34 supplies the resume command, the readcontroller 34 checks whether there is no omission of record data readwith each read system, by ref erring to the second areas of the memories33 ₁ to 33 ₃ used at the present read cycle to confirm that the A-timeone frame before the start A-time data in the second area of the memory33 ₃ is contained in the second area of the memory 33 ₂, and that theA-time one frame before the start A-time data in the second area of thememory 33 ₂ is contained in the second area of the memory 33 ₁.

After the read operation by the optical pickup 2 is performedapproximately I=two rotations (in actual, slightly more than tworotations) and the optical pickup 2 reaches a position VI shown in FIG.8, the contents of the second areas of the memories 33 ₁ to 33 ₃ becomeas shown in FIG. 9 and there is no omission of record data read with theread systems “1, 2, 3”. Therefore, the read controller 34 supplies theintercept command to the write controllers 31 ₁ to 31 ₃ to intercept thewrite operation, and supplies the track jump command to the systemcontroller 50. With reference to the A-time data and the start and endaddresses stored in the second areas among the memories 33 ₁ to 33 ₃where data were written at the present read cycle, the read controller34 controls to read record data in the order of A-time starting from theA-time next to the one block data lastly output to the second signalprocessing circuit 40 at the preceding read cycle, relative to the datastored in the second areas among the memories 32 ₁ to 32 ₃ where dataDATA₁ to DATA₃ were written at the present read cycle, and outputs theread data to the second signal processing circuit 40. In this example,the data from the frame 23:42:00 to the frame 23:43:02 is output.

The write controllers 31 ₁ to 31 ₃ received the intercept commandintercepts the read operation. The system controller 50 received thetrack jump command controls to jump the optical pickup 2 from theposition VI to a position VII shown in FIG. 8. After the light beams 3 ₁to 3 ₃ are focussed in the track-on state on the tracks (x+9), (3+11),and (x+13), reading record data resumes. Thereafter, similar operationsare repeated to read at high speed desired record data from CD-ROM 1 byusing the four beams 3 ₁ to 3 ₃ and by preventing the record data frombeing duplicated and omitted.

(5) Third Specific Read/write Operation (Read Unable by the Light BeamSystems 3 ₄ and 3 ₁, Refer to FIGS. 10 and 9)

If the judgement of a presence/absence of a record data unreadablesystem during one relative rotation of the optical pickup 2 from aposition I shown in FIG. 10 relative to CD-ROM 1, shows that there aretwo record data unreadable systems of the light beams 3 ₄ and 3 ₅, M=3light beams 3 ₁ to 3 ₃ are allocated as the read systems of h lightbeams, where M is the maximum number of adjacent light beam systemsusable, which is “3” or a combination of light beams 3 ₁ to 3 ₃ and M≧2.The continuous read rotation number I is set as I=(c+1)=2, and the readtrack jump number J is set to J={(c+1)·(M−1)−1=3. In accordance with theA-time data representative of the latest A-time data AT₃ input from thefirst signal processing circuit 26 ₃ and the read start point A-timedesignated by the host computer, the track jump direction and number aredetermined so that the light beam 3 ₁ at the innermost circumferenceamong the h=3 read light beams is focussed in the track-on state on thetrack (x−1) one track inner than the track x containing the read startpoint of the A-time.

If the optical pickup 2 is at a position II shown in FIG. 8 after the hread light beam systems are allocated and the continuous read number Iand read track jump number J are set, the optical pickup 2 is jumpedfrom the position II by six tracks in the forward direction so that thelight beams 3 ₁ to 3 ₃ are focussed in the track-on state on the tracks(x−1), (x+1), and (x+3). Then, reading the record data on the tracks(x−1), (x+1) and (x+3) at the same time starts, by using three systemsincluding the photodetector PD₁ to first signal processing circuit 26 ₁,photodetector PD₂ to first signal processing circuit 26 ₂, andphotodetector PD₃ to first signal processing circuit 26 ₃. When all theframe sync detection signals FS₁ to FS₃ are input from the first signalprocessing circuits 26 ₁ to 26 ₃, the specific read/write commandincluding the read system information “1, 2, 3” is supplied to the P/Sconverter 30.

Thereafter, quite similar to the case shown in FIG. 8, an operation ofreading record data from CD-ROM 1 by approximately two rotations,jumping the optical pickup by the track jump number J=3, again readingrecord data from CD-ROM 1 by approximately two rotations, and jumpingthe optical pickup by the track jump number J=3 is repeated (refer toIII to VII in FIG. 10) to read record data at high speed in the recordorder by preventing the record data from being duplicated and omitted.

(6) Fourth Specific Read/write Operation (Read Unable by the Light BeamSystems 3 ₁ and 3 ₅, Refer to FIG. 11)

If the judgement of a presence/absence of a record data unreadablesystem during one relative rotation of the optical pickup 2 from aposition I shown in FIG. 11 relative to CD-ROM 1, shows that there aretwo record data unreadable systems of the light beams 3 ₁ and 3 ₁, M=3light beams 3 ₂ to 3 ₄ are allocated as the read systems of h lightbeams, where M is the maximum number of adjacent light beam systemsusable, which is “3” or a combination of light beams 3 ₂ to 3 ₄ and M≧2.The continuous read rotation number I is set as I=(c+1)=2, and the readtrack jump number J is set to J={(c+1)·(M−1)−1}=3. In accordance withthe A-time data representative of the latest A-time data AT₃ input fromthe first signal processing circuit 26 ₃ and the read start point A-timedesignated by the host computer, the track jump direction and number aredetermined so that the light beam 3 ₂ at the innermost circumferenceamong the h=3 read light beams is focussed in the track-on state on thetrack (x−1) one track inner than the track x containing the read startpoint of the A-time.

If the optical pickup 2 is at a position II shown in FIG. 11 after theh=3 read light beam systems are allocated and the continuous read numberI and read track jump number J are set, the optical pickup 2 is jumpedfrom the position II shown in FIG. 11 by four tracks in the forwarddirection so that the light beams 3 ₂ to 3 ₄ are focussed in thetrack-on state on the tracks (x−1), (x+1), and (x+3). Then, reading therecord data on the tracks (x+1), (x+1) and (x+3) at the same timestarts, by using three systems including the photodetector PD₂ to firstsignal processing circuit 26 ₂, photodetector PD₃ to first signalprocessing circuit 26 ₃, and photodetector PD₄ to first signalprocessing circuit 26 ₄. When all the frame sync detection signals FS₂to FS₄ are input from the first signal processing circuits 26 ₂ to 26 ₄,the specific read/write command including the read system information“2, 3, 4” is supplied to the P/S converter 30.

Thereafter, nearly similar to the case shown in FIG. 8 (in the caseshown in FIG. 11, the write controllers 312 to 31 ₄ control to write thedata DATA₂ to DATA₄ and A-time data AT₂ to AT₄ output from the firstsignal processing circuit 26 ₂ to 26 ₄, into the memories 32 ₂ to 32 ₄and 33 ₂ to 33 ₄, and with reference to the the A-time data and startand end addresses stored in the memories 3 ₃ ₂ to 33 ₄, the readcontroller 34 controls to read record data stored in the memories 33 ₂to 33 ₄ in the order of At-time by preventing the record data from beingduplicated and omitted), an operation of reading record data from CD-ROM1 by approximately two rotations, jumping the optical pickup by thetrack jump number J=3, again reading record data from CD-ROM 1 byapproximately two rotations, and jumping the optical pickup by the trackjump number J=3 is repeated (refer to III to VII in FIG. 11) tosequentially read record data at high speed in the record order bypreventing the record data from being duplicated and omitted.

(7) Fifth Specific Read/write Operation (Read Unable by the Light Beams3 ₂ and 3 ₅, Refer to FIGS. 12 and 13)

If the judgement of a presence/absence of a record data unreadablesystem during one relative rotation of the optical pickup 2 from aposition I shown in FIG. 12 relative to CD-ROM 1, shows that there aretwo record data unreadable systems of the light beams 3 ₂ and 3 ₅, thenonly two light beams 3 ₃ and 3 ₄ are adjacent each other among theremaining three light beams 3 ₁, 3 ₃, and 3 ₄. In reading at high speedrecord data of CD-ROM 1 by repetitively performing continuous recorddata read by approximately two rotations and track jump, it is necessaryto read record data only with adjacent light beams. High speed read ispossible even for a combination of read light beams not completelyadjacent each other, if continuous record data read of CD-ROM 1 by threeor more rotations and track jump by predetermined tracks are repeated.

Specifically, continuously reading record data with data readable lightbeams during approximately {(R+1) (c+1)} rotations and track jump by(Q−1) track can be repeated if Q is 2 or larger and R is 0 or larger,where Q is the number of tracks representing a distance between theinnermost light beam and outermost light beam among the record datareadable light beam systems, and R is the maximum number of adjacentrecord data unreadable light beams between the innermost and outermostrecord data readable light beams.

In the example shown in FIGS. 12 and 13, of the record data readablelight beam systems, the innermost light beam is the light beam 3 ₁ andthe outermost light beam is the light beam 3 ₄ SO that Q=6. In theadjacent record data unreadable light beams between the light beams 3 ₁and 3 ₄, the maximum number of adjacent record data unreadable lightbeams is “1” because there is only the light beam 3 ₂. As the h readlight beam systems, all the three record data readable light beamsystems 3 ₁, 3 ₃, and 3 ₄ are allocated. The continuous read rotationnumber I is set as I={(R+1) (c+1)}=4, and the read track jump number Jis set to J=(Q−1)=5.

If the optical pickup 2 is at a position II shown in FIG. 12 after theh=3 read light beam systems are allocated and the continuous read numberI=2 and read track jump number J=5 are set, the optical pickup 2 isjumped from the position II by six tracks in the forward direction sothat the light beams 3 ₁, 3 ₃, and 3 ₄ are focussed in the track-onstate on the tracks (x−1), (x+3), and (x+5). Then, reading the recorddata on the tracks (x−1), (x+3), and (x+5) at the same time starts, byusing three systems including the photodetector PD₁ to first signalprocessing circuit 26 ₁, photodetector PD₁ to first signal processingcircuit 26 ₃, and photodetector PD₄ to first signal processing circuit26 ₄. When all the frame sync detection signals FS₁, FS₃, and FS₄ areinput from the first signal processing circuits 26 ₁, 26 ₃, and 26 ₄,the specific read/write command including the read system information“1, 3, 4” is supplied to the P/S converter 30.

Upon reception of the specific read/write command via the readcontroller 34, only the write controllers 31 ₁, 31 ₃, and 31 ₄ indicatedby the read system information “1, 3, 4” write one block after anotherthe data DATA₁, DATA₃, and DATA₄ output from the first signal processingcircuits 26 ₁, 26 ₃, and 26 ₄, into the first areas of the memories 32₁, 32 ₃, and 32 ₄, and writes the A-time data AT₁, AT₃, and AT₄corresponding to the data DATA₁, DATA₃, and DATA₄ and the pairs of startaddresses A_(1s) A_(3s) and A_(4s) and end addresses A_(1e), A_(3e) andA_(4e) in the memories 32 ₁, 32 ₃, and 32 ₄, into the first areas of thememories 33 ₁, 33 ₃, and 33 ₄. In the example shown in FIG. 12, in thefirst areas of the memories 33 ₁, 33 ₃, and 33 ₄, the A-time data iswritten from the frames of 23:40:60, 23:41:15, and 23:42:00 (refer toFIG. 13).

The read controller 34 received the specific read/write command checkswhether there is no omission of record data read with each read system,by referring to the first areas of the memories 33 ₁, 33 ₃, and 33 ₄indicated by the read system information “1, 3, 4” and used at thepresent read cycle to confirm that the A-time one frame before the startA-time data in the first area of the memory 33 ₄ is contained in thefirst area of the memory 33 ₃, and that the A-time one frame before thestart A-time data in the first area of the memory 33 ₃ is contained inthe first area of the memory 33 ₁.

After the read operation by the optical pickup 2 is performedapproximately I=four rotations (in actual, slightly more than fourrotations) and the optical pickup 2 reaches a position IV shown in FIG.12, the contents of the first areas of the memories 33 ₁, 33 ₃, and 33 ₄become as shown in FIG. 13 and there is no omission of record data readwith the read systems. Therefore, the read controller 34 supplies theintercept command to the write controllers 31 ₁, 31 ₃, and 31 ₄ tointercept the write operation, and supplies the track jump command tothe system controller 50. With reference to the A-time data and thestart and end addresses stored in the first areas among the memories 33₁, 33 ₃, and 33 ₄, the read controller 34 controls to read record datain the order of A-time starting from the oldest A-time, relative to thedata stored in the first areas among the memories 33 ₁, 33 ₃, and 33 ₄,and outputs the read data to the second signal processing circuit 40. Inthis example, the data from the frame 23:40:60 to the frame 23:42:50 isoutput.

The write controllers 31 ₁, 31 ₃, and 31 ₄ received the interceptcommand intercepts the read operation, and the system controller 50received the track jump command supplies the servo circuit 23 with thetrack jump command indicating a track jump by J=5 tracks in the forwarddirection to thereby jump the optical pickup 2 from the position IV to aposition V shown in FIG. 12. After the light beams 3 ₁, 3 ₃ and 3 ₄ arefocussed in the track-on state on the tracks (x+8), (x+12), and (x+14),reading record data resumes. When all the frame sync detection signalsFS₁, FS₃, and FS₅ of H level are output from the first signal processingcircuits 26 ₁, 26 ₃, and 26 ₄, the track jump completion notice is readand supplied to the controller 34.

The controller 34 received the track jump completion notice supplies theresume command to the write controllers 31 ₁, 31 ₃, and 31 ₄, and thewrite controllers 31 ₁, 31 ₃, and 31 ₄ received the resume command writethe data DATA₁, DATA₃, and DATA₄ output from the first signal processingcircuits 26 ₁, 26 ₃, and 26 ₄ after the track jump, this time into thesecond areas of the memories 32 ₁, 32 ₃, and 32 ₄, and writes the A-timedata AT₁, AT₃, and AT₄ corresponding to the data DATA₁, DATA₃, and DATA₄and the pairs of start addresses a_(1s), a_(3s), and a_(4s) and endaddresses a_(1e), a_(3e), and a_(4e) in the memories 32 ₁, 32 ₃, and 32₄, into the second areas of the memories 33 ₁ 33 ₃, and 33 ₄. In theexample shown in FIG. 12, in the second areas of the memories 33 ₁, 33₃, and 33 ₄, the A-time data is written from the frames of 23:42:48,23:43:33, and 23:43:63 (refer to FIG. 13).

After the read controller 34 supplies the resume command, the readcontroller 34 checks whether there is no omission of record data readwith each read system, by referring to the second areas of the memories33 ₁, 33 ₃, and 33 ₄ used at the present read cycle to confirm that theA-time one frame before the start A-time data in the second area of thememory 33 ₄ is contained in the second area of the memory 33 ₃, and thatthe A-time one frame before the start A-time data in the second area ofthe memory 33 ₃ is contained in the second area of the memory 33 ₁.

After the read operation by the optical pickup 2 is performedapproximately I=four rotations (in actual, slightly more than fourrotations) and the optical pickup 2 reaches a position VI shown in FIG.12, the contents of the second areas of the memories 33 ₁, 33 ₃, and 33₄ become as shown in FIG. 13 and there is no omission of record dataread with the read systems “1, 3, 4”. Therefore, the read controller 34supplies the intercept command to the write controllers 31 ₁, 31 ₃, and31 ₄ to intercept the write operation, and supplies the track jumpcommand to the system controller 50. With reference to the A-time dataand the start and end addresses stored in the second areas among thememories 33 ₁, 33 ₃, and 33 ₄ where data were written at the presentread cycle, the read controller 34 controls to read record data in theorder of A-time starting from the A-time next to the one block datalastly output to the second signal processing circuit 40 at thepreceding read cycle, relative to the data stored in the second areasamong the memories 32 ₁, 32 ₃, and 32 ₄ where data were written at thepresent read cycle, and outputs the read data to the second signalprocessing circuit 40. In this example, the data from the frame 23:42:60to the frame 23:44:62 is output.

The write controllers 31 ₁, 31 ₃, and 31 ₄ received the interceptcommand intercepts the read operation. The system controller 50 receivedthe track jump command controls to jump the optical pickup 2 by thetrack jump number J=5 from the position VI to a position VII shown inFIG. 12. Thereafter, reading record data resumes. Thereafter, similaroperations are repeated to read at high speed desired record data fromCD-ROM 1 by using the three beams 3 ₁, 3 ₃, and 3 ₄ and by preventingthe record data from being duplicated and omitted.

For example, in order to read the record data from the 19 tracks fromthe track (x−1) to the track (x+17) shown in FIG. 12, only reading therecord data of CD-ROM 1 during eight rotations and one track jump arerequired. Therefore, the record data can be read more rapidly than datais read with one light beam from CD-ROM 1 during 19 rotations.

(8) Sixth Specific Read/write Operation (Read Unable by the Light Beams3 ₁, 3 ₂, and 3 ₄, Refer to FIG. 14)

If the judgement of a presence/absence of a record data unreadablesystem during one relative rotation of the optical pickup 2 from aposition I shown in FIG. 14 relative to CD-ROM 1, shows that there arethree record data unreadable systems of the light beams 3 ₁, 3 ₂, and 3₄, then reading record data with adjacent two light beam systems isimpossible. However, similar to the case shown in FIG. 12, continuouslyreading record data with data readable light beams during approximately{(R+1)·(c+1)} rotations and track jump by (Q−1) track can be repeated ifQ is 2 or larger and R is 0 or larger, where Q is the number of tracksrepresenting a distance between the innermost light beam and outermostlight beam among the record data readable light beam systems, and R isthe maximum number of adjacent record data unreadable light beamsbetween the innermost and outermost record data readable light beams.

In the example shown in FIG. 14, of the record data readable light beamsystems, the innermost light beam is the light beam 3 ₃ and theoutermost light beam is the light beam 3 ₅ so that Q=4. In the adjacentrecord data unreadable light beams between the light beams 3 ₃ and 3 ₅,the maximum number of adjacent record data unreadable light beams is “1”because there is only the light beam 3 ₄. As the h read light beamsystems, all the two record data readable light beam systems 3 ₃ and 3 ₅are allocated. The continuous read rotation number I is set as I {(R+1)(c+1)}=4, and the read track jump number J is set to J=(Q−1)=3.

If the optical pickup 2 is at a position II shown in FIG. 14 after theh=2 read light beam systems are allocated and the continuous read numberI=4 and read track jump number J=3 are set, the optical pickup 2 isjumped from the position II by two tracks in the forward direction sothat the light beams 3 ₁, 3 ₃, and 3 ₄ are focussed in the track-onstate on the tracks (x−1), and (x+3). Then, reading the record data onthe tracks (x−1), and (x+3) at the same time starts, by using twosystems including the photodetector PD₃ to first signal processingcircuit 26 ₃, and photodetector PD₅ to first signal processing circuit26 ₅. When all the frame sync detection signals FS₃ and FS₅ are inputfrom the first signal processing circuits 26 ₃ and 26 ₅, the specificread/write command including the read system information “3, 5” issupplied to the P/S converter 30.

Thereafter, nearly similar to the case shown in FIG. 12 (in the caseshown in FIG. 14, the write controllers 31 ₃ and 31 ₅ control to writethe data DATA₃ and DATA₅ and A-time data AT₃ and AT₅ output from thefirst signal processing circuit 26 ₃ and 26 ₅, into the memories 32 ₃and 32 ₅ and 33 ₃ to 33 ₅, and with reference to the the A-time data andstart and end addresses stored in the memories 33 ₃ and 33 ₅, the readcontroller 34 controls to read record data stored in the memories 33 ₃and 33 ₅ in the order of At-time by preventing the record data frombeing duplicated and omitted), an operation of reading record data fromCD-ROM 1 by approximately I=4 rotations, jumping the optical pickup bythe track jump number J=3, again reading record data from CD-ROM 1 byapproximately I=4 rotations, and jumping the optical pickup by the trackjump number J=3 is repeated (refer to III to VII in FIG. 14) tosequentially read record data at high speed in the record order bypreventing the record data from being duplicated and omitted.

For example, in order to read the record data from the 16 tracks fromthe track (x−1) to the track (x+14) shown in FIG. 14, only reading therecord data of CD-ROM 1 during eight rotations and one track jump arerequired. Therefore, the record data can be read more rapidly than datais read with one light beam from CD-ROM 1 during 16 rotations.

(9) Seventh Specific Read/write Operation (Read Unable by the Light Beam3 ₄, Refer to FIG. 15)

If the judgement of a presence/absence of a record data unreadablesystem during one relative rotation of the optical pickup 2 from aposition I shown in FIG. 15 relative to CD-ROM 1, shows that there isone record data unreadable system of the light beam 3 ₄, then readingrecord data with adjacent three light beam systems is possible asdescribed in the above case (4) (refer to FIG. 8). However, if a similaroperation to the case shown in FIG. 12 is incorporated, record data canbe read more quickly.

In the example shown in FIG. 15, of the record data readable light beamsystems, the innermost light beam is the light beam 3 ₅ and theoutermost light beam is the light beam 3 ₅ so that Q=8. In the adjacentrecord data unreadable light beams between the light beams 3 ₁ and 3 ₅,the maximum number of adjacent record data unreadable light beams is R=1because there is only the light beam 3 ₄. As the h read light beamsystems, all the four record data readable light beam systems 3 ₁ to 3₃, and 3 ₅ are allocated. The continuous read rotation number I is setas I={(R+1)·(c+1)}4, and the read track jump number J is set toJ=(Q−1)=3.

If the optical pickup 2 is at a position II shown in FIG. 15 after theh=4 read light beam systems are allocated and the continuous read numberI=4 and read track jump number J=3 are set, the optical pickup 2 isjumped from the position II shown in FIG. 15 by six tracks in theforward direction so that the light beams 3 ₁ to 3 ₃, and 3 ₅ arefocussed in the track-on state on the tracks (x−1), (x+1), (x+3), and(x+7). Then, reading the record data on the tracks (x−1), (x+1), (x+3),and (x+7) at the same time starts, by using four systems including thephotodetector PD₁ to first signal processing circuit 26 ₁, photodetectorPD₂ to first signal processing circuit 26 ₂, photodetector PD₃ to firstsignal processing circuit 26 ₃, and photodetector PD₅ to first signalprocessing circuit 26 ₅. When all the frame sync detection signals FS₃to PS₃, and FS₅ are input from the first signal processing circuits 26 ₁to 26 ₃ and 26 ₅, the specific read/write command including the readsystem information “1, 2, 3, 5” is supplied to the P/S converter 30.

Thereafter, nearly similar to the case shown in FIG. 12 (in the caseshown in FIG. 15, the write controllers 31 ₁ to 31 ₃, and 31 ₅ controlto write the data DATA₁ to DATA₃, and DATA₅ and A-time data AT₁ to AT₃,and AT₅ output from the first signal processing circuit 26 ₁ to 26 ₃,and 26 ₅, into the memories 32 ₁ to 32 ₃, and 32 ₂, and 33 ₁ to 33 ₃,and 33 ₅, and with reference to the the A-time data and start and endaddresses stored in the memories 33 ₁ to 33 ₃, and 33 ₅, the readcontroller 34 controls to read record data stored in the memories 33 ₁to 33 ₃, and 33 ₅ in the order of At-time by preventing the record datafrom being duplicated and omitted), an operation of reading record datafrom CD-ROM 1 by approximately I=4 rotations, jumping the optical pickupby the track jump number J=3, again reading record data from CD-ROM 1 byapproximately I=4 rotations, and jumping the optical pickup by the trackjump number J=3 is repeated (refer to III to VII in FIG. 15) tosequentially read record data at high speed in the record order bypreventing the record data from being duplicated and omitted.

For example, in order to read the record data from the 23 tracks fromthe track (x−1) to the track (x+21) shown in FIG. 15, only reading therecord data of CD-ROM 1 during eight rotations and one track jump arerequired. In contrast, in the case shown in FIG. 8, reading the recorddata of CD-ROM 1 during eight rotations and three track jumps.

(10) Eighth Specific Read/write Operation (Read Unable by the LightBeams 3 ₁, 3 ₄, and 3 ₅, Refer to FIGS. 16 and 17)

If the judgement of a presence/absence of a record data unreadablesystem during one relative rotation of the optical pickup 2 from aposition I shown in FIG. 16 relative to CD-ROM 1, shows that there arethree record data unreadable systems of the light beams 3 ₁, 3 ₄, and 3₅, even with the remaining two adjacent light beams 3 ₂ and 3 ₃, recorddata can be read by repetitively performing data read of CD-ROM 1 duringtwo rotations and track jump in the forward direction.

Specifically, continuously reading record data with data readable lightbeams during approximately {(R+1) (c+1)) rotations and track jump by(Q−1) track can be repeated if Q is 2 or larger and R is 0 or larger,where Q is the number of tracks representing a distance between theinnermost light beam and outermost light beam among the record datareadable light beam systems, and R is the maximum number of adjacentrecord data unreadable light beams between the innermost and outermostrecord data readable light beams.

In the example shown in FIGS. 16 and 17, of the record data readablelight beam systems, the innermost light beam is the light beam 3 ₂ andthe outermost light beam is the light beam 3 ₃ SO that Q=2. In theadjacent record data unreadable light beams between the light beams 3 ₂and 3 ₃, the maximum number of adjacent record data unreadable lightbeams is R=0 because there is no light beam. As the h read light beamsystems, all the two record data readable light beam systems 3 ₂ and 3 ₃are allocated. The continuous read rotation number I is set asI=((R+1)·(c+1)}=2 and the read track jump number J is set to J=(Q−1)=1.

If the optical pickup 2 is at a position II shown in FIG. 16 after theh=4 read light beam systems are located and the continuous read numberI=4 and read rack jump number J=3 are set, the optical pickup 2 isjumped from the position II shown in FIG. 16 by four tracks in theforward direction so that the light beams 3 ₂ and 3 ₃ are focussed inthe track-on state on the tracks (x−1) and (x+1). Then, reading therecord data on the tracks (x−1) and (x+1) at the same time starts, byusing two systems including the photodetector PD₂ to first signalprocessing circuit 26 ₂ and photodetector PD₃ to first signal processingcircuit 26 ₃. When all the frame sync detection signals FS₂ and FS₃ areinput from the first signal processing circuits 26 ₂ and 26 ₃, thespecific read/write command including the read system information “2, 3”is supplied to the P/S converter 30.

Upon reception of the specific read/write command via the readcontroller 34, only the write controllers 31 ₂ and 31 ₃ indicated by theread system information “2, 3” write one block after another the dataDATA₂ and DATA₃ output from the first signal processing circuits 26 ₂and 26 ₃, into the first areas of the memories 32 ₂ and 32 ₃, and writesthe A-time data AT₂ and AT₃ corresponding to the data DATA₂ and DATA₃and the pairs of start addresses A_(2s). and A_(3s) and end addressesA_(2e) and A_(3e) in the memories 32 ₂ and 32 ₃, into the first areas ofthe memories 33 ₂ and 33 ₃. In the example shown in FIG. 16, in thefirst areas of the memories 33 ₂ and 33 ₃, the A-time data is writtenfrom the frames of 23:40:60 and 23:41:15 (refer to FIG. 17).

The read controller 34 received the specific read/write command checkswhether there is no omission of record data read with each read system,by referring to the first areas of the memories 33 ₂ and 33 ₃ indicatedby the read system information “2, 3” and used at the present read cycleto confirm that the A-time one frame before the start A-time data in thefirst area of the memory 33 ₃ is contained in the first area of thememory 33 ₂.

After the read operation by the optical pickup 2 is performedapproximately I=two rotations (in actual, slightly more than tworotations) and the optical pickup 2 reaches a position IV shown in FIG.16, the contents of the first areas of the memories 33 ₂ and 33 ₃ becomeas shown in FIG. 17 and there is no omission of record data read withthe read systems. Therefore, the read controller 34 supplies theintercept command to the write controllers 31 ₂ and 31 ₃ to interceptthe write operation, and supplies the track jump command to the systemcontroller 50. With reference to the A-time data and the start and endaddresses stored in the first areas among the memories 33 ₂ and 33 ₃,the read controller 34 controls to read record data in the order ofA-time starting from the oldest A-time, relative to the data stored inthe first areas among the memories 32 ₂ and 32 ₃, and outputs the readdata to the second signal processing circuit 40. In this example, thedata from the frame 23:40:60 to the frame 23:41:44 is output.

The write controllers 31 ₂ and 31 ₃ received the intercept commandintercepts the read operation, and the system controller 50 received thetrack jump command supplies the servo circuit 23 with the track jumpcommand indicating a track jump by J=1 track in the forward direction tothereby jump the optical pickup 2 from the position IV to a position Vshown in FIG. 16. After the light beams 3 ₂ and 3 ₃ are focussed in thetrack-on state on the tracks (x+2) and (x+4), reading record dataresumes. When all the frame sync detection signals FS₂ and FS₂ of Hlevel are output from the first signal processing circuits 26 ₂ and 26₃, the track jump completion notice is read and supplied to thecontroller 34.

The controller 34 received the track jump completion notice supplies theresume command to the write controllers 31 ₂ and 31 ₃, and the writecontrollers 31 ₂ and 31 ₃ received the resume command write the dataDATA₂ and DATA₃ output from the first signal processing circuits 26 ₂and 26 ₃ after the track jump, this time into the second areas of thememories 32 ₂ and 32 ₃, and writes the A-time data AT₂ and AT₃corresponding to the data DATA₂ and DATA₃ and the pairs of startaddresses a_(2s) and a_(3s) and end addresses a_(2e) and a_(3e) in thememories 32 ₂ and 32 ₃, into the second areas of the memories 33 ₂ and33 ₃. In the example shown in FIG. 16, in the second areas of thememories 33 ₂ and 33 ₃, the A-time data is written from the frames of23:41:=and 23:41:62 (refer to FIG. 17).

After the read controller 34 supplies the resume command, the readcontroller 34 checks whether there is no omission of record data readwith each read system, by referring to the second areas of the memories33 ₂ and 33 ₃ used at the present read cycle to confirm that the A-timeone frame before the start A-time data in the second area of the memory33 ₃ is contained in the second area of the memory 33 ₂.

After the read operation by the optical pickup 2 is performedapproximately I=two rotations (in actual, slightly more than tworotations) and the optical pickup 2 reaches a position VI shown in FIG.16, the contents of the second areas of the memories 33 ₁, 33 ₃, and 33₄ become as shown in FIG. 17 and there is no omission of record dataread with the read systems “2, 3”. Therefore, the read controller 34supplies the intercept command to the write controllers 31 ₂ and 31 ₃ tointercept the write operation, and supplies the track jump command tothe system controller 50. With reference to the A-time data and thestart and end addresses stored in the second areas among the memories 33₂ and 33 ₃ where data were written at the present read cycle, the readcontroller 34 controls to read record data in the order of A-timestarting from the A-time next to the one block data lastly output to thesecond signal processing circuit 40 at the preceding read cycle,relative to the data stored in the second areas among the memories 32 ₂and 32 ₃ where data were written at the present read cycle, and outputsthe read data to the second signal processing circuit 40. In thisexample, the data from the frame 23:41:45 to the frame 23:42:16 isoutput.

The write controllers 31 ₂ and 31 ₃ received the intercept commandintercepts the read operation. The system controller 50 received thetrack jump command controls to jump the optical pickup 2 by the trackjump number J=1 from the position VI to a position VII shown in FIG. 16.Thereafter, reading record data resumes. Thereafter, similar operationsare repeated to read at high speed desired record data from CD-ROM 1 byusing the three beams 3 ₂ and 3 ₃ and by preventing the record data frombeing duplicated and omitted.

(11) Ninth Specific Read/write Operation (Read Unable by the Light Beams3 ₁, 3 ₂, 3 ₄, and 3 ₅, Refer to FIGS. 18 and 19)

If the judgement of a presence/absence of a record data unreadablesystem during one relative rotation of the optical pickup 2 from aposition I shown in FIG. 18 relative to CD-ROM 1, shows that there arefour record data unreadable systems of the light beams 3 ₁, 3 ₂, 3 ₄,and 3 ₅, record data is omitted if it is read with only one light beam 3₃ by repetitively performing data read of CD-ROM 1 during two rotationsor more and track jump in the forward direction. In this case, recorddata is continuously read from CD-ROM 1 by using the record datareadable one light beam system.

Specifically, as the h read light beam systems, the record data readablelight beam 3 ₃ is allocated. The continuous read rotation number I isset as infinite, and the read track jump number J is set to J=0.

If the optical pickup 2 is at a position II shown in FIG. 18 after theh=1 read light beam system is allocated and the continuous read numberI=infinite and read track jump number J=1 are set, the optical pickup 2is jumped from the position II shown in FIG. 18 by two tracks in theforward direction so that the light beams 3 ₃ is focussed in thetrack-on state on the track (x−1). Then, reading the record data on thetrack (x−1) starts, by using one system of the photodetector PD₃ tofirst signal processing circuit 26 ₃. When the frame sync detectionsignal FS₃ is input from the first signal processing circuits 26 ₃, thespecific read/write command including the read system information “3” issupplied to the P/S converter 30.

Upon reception of the specific read/write command via the readcontroller 34, only the write controller 31 ₃ indicated by the readsystem information “3” writes one block after another the data DATA₃output from the first signal processing circuits 26 ₃, into the firstarea of the memory 32 ₃, and writes the A-time data AT₃ corresponding tothe data DATA₃ and the pairs of start addresses A_(3s) and end addressesA_(3e) in the memory 32 ₃, into the first area of the memory 33 ₃. Inthe example shown in FIG. 18, in the first area of the memory 33 ₃, theA-time data is written from the frame of 23:40:60 (refer to FIG. 19).After data is written in the end regions of the first areas of thememories 32 ₃ and 33 ₃, the start regions of the first areas areautomatically reserved for continuing data write.

Since only one piece of the read system information “3” is used, theread controller 34 received the specific read/write command refers tothe first areas of the memories 33 ₃ indicated by the read systeminformation “3” and used at the present read cycle, and controls to readrecord data in the order of A-time starting from the oldest A-time,relative to the data stored in the first areas of the memory 32 ₃, andoutputs the read data to the second signal processing circuit 40,without issuing the intercept command and track jump command. Therefore,during data read, the optical pickup 2 will not jump (refer to III to VIin FIG. 18), and as CD-ROM 1 rotates, the record data after the track(x−1) can be read with the light beam 3 ₃ system without any omission ofrecord data and supplied to the second signal processing circuit 40.

In the above embodiments, different beams 3 ₁ to 3 _(n) are applied atthe same time to every (c+1)-th tracks of CD-ROM 1, where c=1 and n=5.The invention is not limited only to the above embodiments, othercombinations of c and n may also be used if c is an integer “1” orlarger and n is an integer “2” or larger. For example, an optical pickup2B shown in FIG. 20-1 may apply three light beams 31 to 3 ₃ to tracks atevery second, or an optical pickup 2C shown in FIG. 20-2 may apply threelight beams 3 ₁ to 3 ₃ to tracks at every third.

With the optical pickup shown in FIG. 20-1, if there is no record dataunreadable light beam system, record data of CD-ROM 1 is read byrepeating an operation of continuous read of the record data with threelight beam systems 3 ₁ to 3 ₃ during approximately (c+1)=2 rotations ofCD-ROM 1 and track jump by {(c+1) (n−1)−1}=3 tracks in the forwarddirection after it is confirmed that there is no omission of record dataread from CD-ROM 1 with a combination of three light beams 3 ₁ to 3 ₃.Similarly, with the optical pickup shown in FIG. 20-2, if there is norecord data unreadable light beam system, record data of CD-ROM 1 isread by repeating an operation of continuous read of the record datawith three light beam systems 3 ₅ to 3 ₃ during approximately (c+1)=3rotations of CD-ROM 1 and track jump by ((c+1) (n−1)−1}=5 tracks in theforward direction after it is confirmed that there is no omission ofrecord data read from CD-ROM 1 with a combination of three light beams 3₁ to 3 ₃.

With the optical pickup shown in FIG. 20-1, if there is a record dataunreadable light beam system, e.g., the light beam system 3 ₃, M is “2”including the two light beams 3 ₁ and 3 ₂ where M is the maximum numberof adjacent record data readable light beam systems among the remaininglight beam systems. The M=2 light beams systems 3 ₁ and 3 ₂ areallocated as the read light beam systems. In this case, record data ofCD-ROM 1 is read by repeating an operation of continuous read of therecord data with the allocated two light beam systems 3 ₁ and 3 ₂ duringapproximately (c+1) =2 rotations of CD-ROM 1 and track jump by{(c+1)·(M−1)−1}=1 track in the forward direction after it is confirmedthat there is no omission of record data read from CD-ROM 1 with acombination of two light beams 3 ₁ and 3 ₂.

Similarly, with the optical pickup shown in FIG. 20-2, if there is arecord data unreadable light beam system, .e.g., the light beam system 3₃, M is “2” including the two light beams 3 ₁ and 3 ₂ where M is themaximum number of adjacent record data readable light beam systems amongthe remaining light beam systems. The M=2 light beams systems 3 ₁ and 3₂ are allocated as the read light beam systems. In this case, recorddata of CD-ROM 1 is read by repeating an operation of continuous read ofthe record data with the allocated two light beam systems 3 ₁ and 3 ₂during approximately (c+1)=3 rotations of CD-ROM 1 and track jump by{(c+1)·(M−1)−1}=2 tracks in the forward direction after it is confirmedthat there is no omission of record data read from CD-ROM 1 with acombination of two light beams 3 ₁ and 3 ₂.

In the description of the case (3) (refer to FIGS. 6 and 7), the lightbeam system 3 ₅ is unable to read record data and the maximum number Mof adjacent record data readable light beam systems is “4” and M≧2.Therefore, as the h record data light beams systems, the M=4 light beams3 ₁ to 3 ₄ are allocated, and the continuous read rotation number I isset to I=(c+1)=2, and the track jump number J is set toJ={(c+1)·(M−1)−1}5. Instead, the continuous read rotation number I maybe set to I={(R+1)·(c+1)}=2 and the track jump number J may be set toJ=(Q−1)=5, where Q is the number of tracks representing a distancebetween the innermost light beam and outermost light beam among theallocated h=4 record data readable light beam systems 3 ₁ to 3 ₄ and inthis case Q=6, and R is the maximum number of adjacent record dataunreadable light beams between the innermost and outermost record datareadable light beams among the the allocated h=4 record data readablelight beam systems 3 ₁ to 3 ₄ and in this case R=0.

In the description of the case (4) (refer to FIGS. 8 and 9), the lightbeam system 3 ₄ is unable to read record data and the maximum number Mof adjacent record data readable light beam systems is “3”. Therefore,as the h record data light beams systems, the M=3 light beams 3 ₁ to 3 ₃are allocated, and the continuous read rotation number I is set toI=(C+1)=2, and the track jump number J is set to J={(c+1)·(M−1)−1}=3.Instead, the continuous read rotation number I may be set toI={(R+1)·(c+1)}=2 and the track jump number J may be set to J=(Q−1)=3,where Q is the number of tracks representing a distance between theinnermost light beam and outermost light beam among the allocated hrecord data readable light beam systems 3 ₁ to 3 ₃ and in this case Q=4,and R is the maximum number of adjacent record data unreadable lightbeams between the innermost and outermost record data readable lightbeams among the the allocated h record data readable light beam systems3 ₁ to 3 ₃ and in this case R=0.

Similarly, in the cases ((5) or (6), the continuous read rotation numberI may be set to I={(R+1)·(c+1)}=2 and the track jump number J may be setto J=(Q−1)=3, where Q is the number of tracks representing a distancebetween the innermost light beam and outermost light beam among theallocated h=3 record data readable light beam systems 3 ₁ to 3 ₃ or 3 ₂to 3 ₄ and in this case Q=4, and R is the maximum number of adjacentrecord data unreadable light beams between the innermost and outermostrecord data readable light beams among the the allocated h=3 record datareadable light beam systems 3 ₁ to 3 ₃ or 3 ₂ to 3 ₄ and in this caseR=0.

In the description of the case (10) (refer to FIGS. 16 and 17), thereare three record data unreadable light beam systems 3 ₁, 3 ₄, and 3 ₅,the continuous read rotation number I is set to I={(R+1)·(c+1)}=2 andthe track jump number 3 may be set to J=(Q−1)=1, where Q is the numberof tracks representing a distance between the innermost light beam andoutermost light beam among the record data readable light beam systems 3₂ and 3 ₃ and in this case Q=2, and R is the maximum number of adjacentrecord data unreadable light beams between the innermost and outermostrecord data readable light beams among the the allocated record datareadable light beam systems and in this case R=0. Instead, since themaximum number M of adjacent record data readable light beam systems is“2”, as the h record data light beams systems, the M=2 light beams 3 ₂and 3 ₃ may be allocated, and the continuous read rotation number I maybe set to I=(c+1)=2, and the track jump number J may be set to J{(c+1)·(M−1)−1}=1.

In the above embodiments, a presence/absence of a record data unreadablelight beam system is judged at the track position one track before theread start point designated by the host computer, and in accordance withthe judgement result, the h read light beam systems, the continuous readrotation number I, and the track jump number J are set. Thereafter, theoptical head is jumped to the track immediately before the read startpoint to start reading record data. Instead, a presence/absence of arecord data unreadable light beam system may be judged at the trackposition containing the read start point, or at the lead-in of theinnermost circumference of CD-ROM 1.

In the cases (3) to (9) and the case shown in FIG. 20, if it is judgedthat there is some record data unreadable light beam systems, the systemcontroller 50 selects from the remaining record data readable light beamsystems a combination of two or more light beam systems, and allocatesthe combination as as the h read light beam systems, to thereafter setthe continuous read rotation number I and the track jump number J inaccordance with predetermined rules. However, the continuous readrotation number R when the continuous read of CD-ROM 1 with acombination of the allocated h read light beam systems is performeduntil omission of the record data becomes none, can be automaticallydetermined as approximately {(R+1) (c+1)} where R is the maximum numberof adjacent record data unreadable light beams between the innermost andoutermost record data readable light beams among the the h read lightbeam systems. Therefore, only the track jump number J may be set. Thecontinuous read rotation number when the continuous read of CD-ROM 1with a combination of all the n optical light beam systems is performeduntil omission of the record data becomes none, can also beautomatically determined as approximately (c+1).

Also in the above embodiments, although CD-ROM is rotated at a constantlinear velocity, it may be rotated at a constant angular velocity (CAV).Other optical discs with a spiral track of the type different fromCD-ROM may also be used such as CD-WO, DVD, DVD-ROM and DVD-RAM.

What is claimed is:
 1. An optical disc read method of reading datarecorded on tracks of an optical disc formed with a spiral track with nlight beam systems for applying different light beams 1, . . . , i, . .. , n at the same time to n tracks at every (c+1)-th and independentlydetecting the light beams reflected from the optical disc, where c is aninteger of 1 or larger and n is an integer of 2 or larger, characterizedin that; if there is a light beam system or systems incapable of readingthe record data of the optical disc, the record data of the optical discis read by alternately performing a continuous reading operation forapproximately (c+1) rotations and a track jump operation forapproximately {(c+1)·M−1)−1} tracks in a forward direction after saidcontinuous reading operation, by only using detection outputs from agroup of M (M<n) adjacently arranged light beam systems capable ofreading the record data.
 2. An optical disc read method according toclaim 1, wherein said group is the most populous group of adjacentlyarranged light beam system capable of reading the record data.
 3. Anoptical disc read method of reading data recorded on tracks of anoptical disc formed with a spiral track with n beam systems for applyingdifferent light beams 1, i, . . . , n at the same time to n tracks atevery (c+1)-th and independently detecting the light beams reflectedfrom the optical disc, where c is an integer of 1 or larger and n is aninteger of 2 or larger, characterized in that; if there is a light beamsystem or systems incapable of reading the record data of the opticaldisc, where Q is the number of tracks representing a distance betweenthe innermost light beam system and outermost light beam system amonglight beam systems capable of reading the record data and R is thenumber of the most populous group of adjacently arranged light beamsystems incapable of reading the record data between the innermost andoutermost light beams systems able to read the record data, the recorddata of the optical disc is read by alternately performing a continuousreading operation for approximately {(R+1)·(c+1)} rotations and a trackjump operation for approximately (Q−1) tracks in a forward directionafter said continuous reading operation, by using detection output fromthe light beam systems capable of reading the record data.
 4. An opticaldisc read method according to claim 3, wherein the record data detectedfrom the tracks of the optical disc during said continuous readingoperation is stored together with frame addresses, and said track jumpoperation is performed when a frame address corresponding to the recorddata read with the i-th light beam becomes continuous with a continuousdata read start frame address corresponding to the record data to beread with the adjacent (i+1)-th light beam.
 5. An optical disc readapparatus comprising: n light beam systems for applying different lightbeams 1, . . . , i, . . . , n at the same time to n tracks at every(c+1) -th of an optical disc with a spiral track and independentlydetecting the light beams reflected from the optical disc, where c is aninteger of 1 or larger and n is an integer of 2 or larger, and forreading record data recorded on the optical disc independently for eachof n light beams; and read control means for controlling said light beamsystems to read the record data of the optical disc by alternatelyperforming a continuous reading operation and a track jump operation,characterized in that; said control means controls said light beamsystems so that if there is a light beam system or systems incapable ofreading the record data of the optical disc, the record data of theoptical disc is read by alternately performing a continuous readingoperation for approximately (c+1) rotations and a track jump operationfor approximately {(c+1)·(M−1)−1} tracks in a forward direction aftersaid continuous reading operation, by only using detection outputs froma group of M (M<n) adjacently arranged light beam systems capable ofreading the record data.
 6. An optical disc read apparatus comprising: nlight beam systems for applying different light beams 1, . . . , i, n atthe same time to n tracks at every (c+1)-th of an optical disc with aspiral track and independently detecting the light beams reflected fromthe optical disc, where c is an integer of 1 or larger and n is aninteger of 2 or larger, and for reading record data recorded on theoptical disc independently for each of n light beams; and read controlmeans for controlling said light beam systems to read the record data ofthe optical disc by alternately performing a continuous readingoperation and a track jump operation, characterized in that; saidcontrol means controls said light beam systems so that if there is alight beam system or systems incapable of reading the record data of theoptical disc, where Q is the number of tracks representing a distancebetween the innermost light beam system and outermost light beam systemamong light beam systems capable of reading the record data and R is thenumber of the most populous group of adjacently arranged light beamsystems incapable of reading the record data between the innermost andoutermost light beam systems able to read the record data, the recorddata of the optical disc is read by alternately performing a continuousreading operation for approximately {(R+1)·(c+1)} rotations and a trackjump operation for approximately (Q−1) tracks in a forward directionafter said continuous reading operation, by using detection output fromthe light beam systems capable of reading the record data.